Outside of combat, an artificer's monocle is a good investment (as it is for any artificer); I'd also look into wands of generic skill-booster effects like Greater Heroism for that extra edge. (You can create scrolls or potions of the basic Heroism effect on your own.) Eternal Wands are always useful too, but in your case (since you don't fight that much) you don't need the Heroics wand I keep suggesting on showcased builds; Invisibility, Knock, Shatter, Shrink Item and Rope Trick are good candidates instead, as are just about any of the low-level figments. (Any of these you don't expect to use all that often can be covered with Spell Storing Item instead.) You're an infiltrator, act like one!

One particularly interesting choice of item is a Desert Wind cloak keyed to a hilariously under-used maneuver: Distracting Ember. This maneuver creates a flanking partner for one round, and is obviously intended to allow swordsages to support rogues (or themselves, if they're Shadow Hand focused), but it does so by actually summoning a physical creature for one round. For you, this does two things: It creates a second target for you to divert enemy attention towards (although due to action costs, it'll only work against attacks of opportunity with Fade into Violence; if the elemental lasted until the start of your next turn its options would be much more interesting), and, more importantly, it allows you to remotely trigger your traps from a distance if it looks like your target isn't getting close enough. (Several traps have an area of effect; if your target is in an adjacent square but isn't likely to step on the trigger, Distracting Ember can create a fire elemental right where you want it, and BOOM, off the trap goes.)

A related item, the assorted Bags of Tricks, can do pretty much the same thing, and - if the critter in question has a threatened area - can provide you with the distraction you need to work your misdirection feats. There are, however, some thematic concerns involved when a wild deer or angry rhinocerous suddenly appears at a dinner party.

One other aspect to look into is equipment that lets you read the minds of your targets, especially if you can extract memories from them. You've got Use Magic Device - if your DM allows this to function as Use Psionic Device (it already doubles as Use Clerical Device and Use Arcane Device, and psi is supposed to be transparent...) you shoud look at the telepath list for this. If you can get this, your feat and feature setup can let you essentially perfectlyassume the identity of existing NPCs in your campaign. I'll let you figure out how much fun this could be - just use your abilities to trap and kidnap someone, mindscan them, and then... showtime.

Another oddball choice is the Immovable Rod. Normally this is expensive and superfluous but old-school players will remember just how much havoc one can wreak with this if you're creative. The classical uses - holding a door veryshut, providing a handhold or foothold in midair, or as part of a larger assembly (such as a fulcrum or holding a platform) are all appropriate to your do-it-yourself nature. An almost trivial direct-combat example is to wait until one of your Equalizer traps knocks a target prone (which, since it does so on your opponent's turn, leaves your actions open), then run on up, set the rod on his back (ideally horizontally across the shoulder blades), and press the button. Good luck standing or rolling away from that!

Since everyone expects this build to be some kind of mechanical genius, I'd be amiss if I didn't mention the obscure, but very very useful, Universal Key. Just be careful if you choose to employ this one in combat - your low Charisma (and likely opponents in a social intrigue game!) mean it's quite easy to turn against you, and while you can finish the battle after your pants have been disassembled, it's just tacky.

The MIC's Ring of Arming also deserves special mention. Minor Change Shape doesn't alter your equipment, just your own appearance. This item acts like a superior version of a Glove of Storing (another good item choice, particularly with Sleight of Hand, but let's focus on the ring for now) in that it can store entire equipment loadouts and switch them all, including full suits of armor, with just a standard action. In a few seconds with this ring, you can go from impersonating a guard in heavy armor to impersonating a noble at the masquerade, or you can switch from a perfectly mundane disguise into full combat gear as soon as you hear "roll for initiative".

Finally, thanks to a submission from ObsidianConspiracy, a Collar of Umbral Metamorphosis (Tome of Magic) is a great complement here, as the Dark template gives you quite a lot of things that you will appreciate, most dramatically Hide in Plain Sight. I'm not sure if Minor Change Shape is enough to cover for the Dark template's physical shifts, so you might want to stick to the normal collar and only activate it when you're going into "battle mode", though. In any case, it's most useful at the later levels, since your uses of the Hide skill aren't actually dependent upon hiding (and, in fact, Shadow Striker depends upon being observed!) and at the late levels you get Darkstalker. You'll still need something to hide behind at first, but you've got a stinkbomb trap for that (which emulates Stinking Cloud, which obscures vision). Deoxhydroxinate also points out that you can easily use a tower shield for this purpose if you can somehow get it deployed quickly enough.

Able Learner requires Human or Doppelganger. It was never explicitly stated that changelings – the children of humans and doppelgangers – qualify for it, but it’s a reasonable assumption that simplifies things easily. (Well, Races of Eberron does flat-out say that changelings like to take the Chameleon class (see page 43!), which requires Able Learner, so it’s pretty strongly implied.)

Social Intuition gives you a lot of good intrigue abilities (mostly doing critical social stunts faster), but importantly it gives Skill Mastery in a lot of skills, including Bluff. We’ll be using that one soon. The rest can be used to wreak some havoc with changeling shapeshifting - +10 to Disguise at level 1 and the ability to take 10 on most of the “keep your cover” skills is great, particularly when that take 10 result is high enough to hit DC 15 (in other words, you casually complete “tough” tasks at level 1).

And, as a side note, the Changeling Rogue substitution levels have a positively amazing 10 skill points per level, which give you 56 skill points to play with at level 1.

“I don’t always botch Disguise checks, but when I do, I prefer Second Impression.”

Trap Sense is generally meh, so there’s no reason to not swap it here, especially given the TEN skill points available to changeling rogues. Minor Lore can sometimes help with cover stories as well. Remember that even if you don’t put any points into Knowledge, this bonus applies to Aid Another attempts as well; eventually your Int mod will be high enough to automatically succeed on those attempts to, so even with 0 Knowledge, you’re a great assistant.

Oh, and why Persona Immersion? Because the most reliable way to see through a disguise in D&D involves mind reading (Read Thoughts, Detect Thoughts, etc. are online as of level 3!) and very few of those effects are over 3rdlevel. (Those that are, such as Mind Probe, tend to be used after your cover is blown.) Persona Immersion is the easiest way to make sure those backfire. The Assume Quirk trick works very nicely with this as well, if you’ve researched your subject enough.

We needed trapfinding from some source, and artificer gets that while providing Intelligence synergy, granting access to good support magic, and counting as a spellcaster (unlocking Craft: Alchemy’s better uses). The much-needed Will save boost is gravy.

Spend some time looking through the low-level spell lists. You’ll be able to scribe spells that require up to CL 4 off of any list, although they only take effect at CL 2. Many of the good infiltration ones aren’t terribly CL-dependent –Ventriloquism and Silence come to mind.

At this point, Spell Storing Item becomes your favorite infusion, if you can get a high enough UMD check to pull it off reliably. While item creation is limited by caster level, this infusion is only limited by spell level, so obscure but amazing prestige lists like the Trapsmith’s (Dungeonscape) become available. Furthermore, you can assemble these tools on the spot once you’ve infiltrated your area, although it normally takes a minute to do so. (Remember that you can spend an action point to speed this up!).

The choice of traps is entirely up to you, since their importance varies based on your game. These ARE your kill moves, though, so as the opportunity arises, upgrade to the deadliest, most crippling ones you can make. Nothing stops you from building multiple traps and placing them in the same square either. Some of them also work rather unusually – for instance, the Equalizer doesn’t use an ability check to knock its victims prone, so Stability won’t help.

Fade into Violence lets you work with an ally to threaten a target, and then – using the Bluff skill you can take 10 on – force the enemy to ignore you in favor of your ally. It's an immediate action as well, so you can use it as a sort of pseudo-counter if someone tries to hit you. This can be used to get free sneak attacks here or to slip away unnoticed, but later on it’ll be a critical part of your offensive strategy. Note that since deploying a trap doesn’t target an enemy (i.e. it wouldn’t break Invisibility), you can still use it while using Fade into Violence. You can sneak up to a guy and trap his shoes. Or, even if he notices you, Fade into Violence can divert his attention elsewhere.

Conceal Spellcasting doesn’t care how long it takes to cast your spell, which means you can now rig up your Spell Storing Items in the middle of a dinner party.

Bring it on! Shadow Striker’s most important option is the Evade Notice, which operates like a better (less-limited) version of Fade into Violence, keyed off of Hide instead. It's only usable if you take no direct hostile action – which setting a trap is not. With an ally to support you, you can easily slip between targets completely unnoticed while rigging up high-DC traps right underfoot.

The other two options aren't useful at all to you, but there are circumstances when you'd want to toy around with them too. Fade Away is probably the only one you'll realistically be using, as you depend strongly on stealth for your defenses.

Second Impression is optional, but it’s one of those very nice skill tricks without a secondary limit (unlike, say, Social Recovery) that also happens to work on large numbers of targets at once. Listen to This is the alternative because it lets you record two close-by conversations.

The real winner is that starting this level, every skill is a class skill. You were already buying them at class-skill rates, but now you have class skill max ranks in all of them.

You’re advancing Combat Trapsmith, natch. Note that this increases its class level for formula purposes, which includes the DC on your traps. You also MIGHT get a trade on the traps (depending on how +1 Class Features is interpreted; we don’t see a reason why it wouldn’t), although you’re still limited to six traps.

Timely Misdirection gives you a way to bypass AoO tanks using Bluff instead of Tumble, except it’ll actually work against those annoying Thicket of Blades users. Think of it as a Bluff-based Douse the Flames or Covering Strike. 

Oh, the feat? It’s just a prerequisite. But you're getting quite a bit of Bluff mileage anyway, and Bluff is awesome regardless.

By combining Timely Misdirection and Group Fake-Out, you can escape from dogpiles or the Danger Zone where two AoO tanks overlap without too much difficulty.

A natural choice for you – spymaster isn’t necessarily the most optimal in a combat game, but it provides a lot of good support for an intrigue game, and lets you get into places you wouldn’t normally be able to get into. Plus, Cover Identity + Persona Immersion + Assume Quirk can lead to some pretty fun impersonation effects if your cover identityis a real NPC. You’d have to abduct him first, but you have enough ways of incapacitating targets already.

Combat Trapping is a single special ability, thus this feat adds its bonus to all your traps. Which now have the same base DC as 9th level spells… except they’re usable at will.

Boom! Wonderful feat, and one I really wish we could have had much earlier. To qualify, you’ll either need a +1 tome or an ability boost into Charisma, but that’s not hard to do by this point.

The first ability gives you the ability to create social diversions for your team to sneak in – not as useful as it sounds, but it complements your abilities well. The SECOND ability is where it shines: Trap of Words will reveal any deliberate deception on the opponent’s part, without relying on any magic, and without the opponent being aware he’s done it. (He might notice he’s let it slip at first, but you’ve got enough Bluff to cover for that possibility.)

Hey, since Deep Cover makes Persona Immersion basically obsolete (after having served its purpose well for many levels), we may as well go for Darkstalker here instead. It’s a great feat, and you’ve got an open slot, so why not throw it in there? Just as your epic disguise checks can foil even True Seeing, now your epic Hide checks can as well (along with a host of other abilities). It’s a shame you can’t get Hide in Plain Sight here, but with Fade Into Violence and Shadow Striker you may not need to. I only wish it could have come online sooner.

There’s a few skills here listed with 0 ranks because of significant synergy bonuses and related spycraft. These final modifiers assume masterwork tools, but no magical equipment beyond the ability boosters already mentioned.
Autohypnosis 5 (+10)
Bluff 23 (+34, Social Intuition, Master Manipulator, Fade into Violence)
Concentration 5 (+10)
Craft (alchemy) 5 (+19)
Craft (trapmaking) 10 (+27)
Diplomacy 16 (+26, Social Intuition, Master Manipulator)
Disable Device 19 (+33)
Disguise 10 (+28, Minor Change Shape)
Escape Artist 0 (+7)
Forgery 5 (+19)
Gather Information 10 (+16, Social Intuition)
Hide 23 (+28, Shadow Striker)
Intimidate 0 (+10, Social Intuition)
Knowledge (Any Three) 1 (+21, Minor Lore) 
Knowlege (The Other Eight) 0 (+20, Minor Lore)
Listen 23 (+25)
Move Silently 20 (+25, Shadow Striker)
Open Lock 5 (+10)
Search 19 (+33)
Sense Motive 20 (+24, Social Intuition, Master Manipulator)
Sleight of Hand 5 (+12)
Spellcraft 1 (+17)
Spot 23 (+25)
Use Rope 5 (+10)
Use Magic Device 23 (+31, Artisan Bonus)

Skill Tricks: 8pts spent, 3 bonus tricks, 3 favored tricks
Artificer Knowledge: +14 vs DC 15 to discern magic auras

A few quick skill notes:

• Autohypnosis has a Memorize feature which works on written or visual material very similarly to how Listen to This works on audio (and Autohypnosis may, in fact, allow you to use Listen to This to recite the "perfect clarity" description, then memorize that for longer-term retention of unusual language recordings). It also has a “Forget” function described in Dragonmarked (page 75; it's essentially Memorize but in reverse) which actually lets you manipulate your memory in the case of a Mind Probe or similar effect. A +4 bonus on this from any source will let you do this without a roll.
• Don’t forget that your insane Bluff also lets you transmit secret information via its Innuendo ability. It isn't telepathy, but it may as well be in circumstances where you're expected to be talking.
• Craft (Trapmaking) doesn’t need as many ranks as you’d think after your Intelligence starts getting up there – you only need to hit DC 28 if you’re trying to build a Great Scorcher trap without any materials, and that’s possible here on a natural 1 assuming no other penalties. While you're levelling up, but after you've met the prereqs, you can get around the lower ranks by employing the trapmaker's kit (a bit costly and bulky but helps keep the DCs down) and masterwork tools.
• This approach lets you pick three appropriate knowledge skills (probably Nobility, Local, and either Arcana or History) to count as trained, but even on the other skills, a +20 modifier with 0 ranks means he knows every single piece of common knowledge out there. If you want to turn this guy into a better knowledge base, pull ranks from somewhere else. (You probably don't need Move Silently quite that high, for instance.) 
• Open Lock isn’t high enough to handle the toughest locks, but it handles most of them. The higher-level ones, such as the hair-ripping-out DC 40 Amazing lock, are tackled via Spell Storing Item creating a charge of knock.
• Don’t forget that Spot has a Read Lips ability and the ability to decode secret information with Bluff. This ability combines hilariously well with Listen to This and your memory stunts on Autohypnosis – essentially, only telepathic communication is protected from you.
• Use Rope is on there because it lets you hog-tie your incapacitated targets if you want to capture them. It’s also useful for grappling hook entrances, rappelling/abseiling escapes, and related non-social infiltration moves – it's one of those skills you appreciate when you have it but no one ever takes ranks. Plus, you get to make awful “James Bondage” jokes.
• Use Magic Device is, as usual, freaking amazing and very, very important to this build. Get a skill booster on here as soon as you can, especially after the artificer levels come online. You need to hit DCs in the low 20s reliably as soon as possible and Charisma isn’t your primary stat. You won't need it in the end-game, but it can make or break your tactics early on.

Remember that this is just one potential skill point loadout, and because of Able Learner and the eventual Uncanny Trickster level, your skill choices are essentially completely unrestricted beyond the prerequisites listed at the start of the build.