Transmogrification: the ability to transform one's current gear in such a way that one can make a current piece of gear look as if it was really another piece of gear (of the same item type).
This new fangled thing called transmogrification (or transmog/mogging/trans/whatever else people call it these days) is going to be the new thing to do come 4.3. Why? That's easy, because finally the players are given a good degree of customization when it comes to their characters. Sure we don't get dyes or anything fancy like that yet, but with transmogrification a player will be able to transform their current piece of gear or item set to look like another piece of gear or item set.
Example: You can transmog Tusked Shoulderpads into Passive Resistor Spaulders, but you'd keep the stats of Tusked Shoulderpads.
So if that tasty upgrade that you finally looted doesn't match the rest of your gear, you're in luck! Come 4.3 you can fix that with a little bit of gold and a visit to your local Ethereal Transmog Specialist.
Generally for H:AE I like to list things out for people. Unfortunately (or fortunately, depending on what side of the fence you're looking in from) the gear database is HUGE. Honestly I don't have the time nor sanity to go through every set available. However, there are several bloggers and sites out there who have been working on projects that focus on just that; categorizing and putting together great sets so players don't have to spend years wading through Wowhead, hoping to find that they're after.
Once upon a time I did actually attempt to put together a weekly/bi-weekly series focusing on gear sets and in game "costumes" that people may enjoy. Some of you may remember the few scant posts I did for the series "The Rack," which did a few profession sets along with a highlight of all of the shaman tier. Then I'm not quite sure what happened. Regardless, I'm not all that great of a source for your transmog needs. You know who is though? The blogs and websites I'm about to link. The people behind these sites have done some fantastic works, so please check them out if you're in need of that perfect Blood Elf mage RP set or if you're curious about all the different leather items available.
World of Wardrobes - First on the list is World of Wardrobes. While you could probably search for many of these items through Wowhead as well, sometimes that search ends up being a bit clunky because stats and level requirements. World of Wardrobes simplifies that. Sin hasn't cataloged everything in game yet, but she's well on her way. You can also find Sin on Twitter @Worldofwardrobe and @sinfullysweet_
Disciplinary Action - That one disco priest is at it again! This time around she's provided and incredibly solid list of several different gear sets, all broken down into iLevel brackets. So far she has completed the cloth and mail collections, so definitely look for the plate and mail versions sometime in the near(ish) future! Find her on Twitter @discopriest
Orcish Army Knife - Generally the goal of someone who is putting together a transmog list is to make things match. Rades for the most part doesn't follow that train of thought. If you're after some serious clown suits, definitely check out the various posts Rades has made on his site with the tag 'Transmog'. If you care to sta...track down Rades on Twitter, you may find him @_rades
A Sunnier Bear - Are you a druid looking for druidy related gear? Sunnier has put together not one, but two wonderful posts for druid-related gear things. If you want to see the actual outfits, check out this post. If you're after those pretty sticks, definitely check out this post. If you're interesting in seeing what Sunnier has to tweet about, you can find her @SunnierBear
Disenchanting Azeroth - Looking for weaponry of various sorts? This site just may be able to help you out. Everything is shown on this site by breaking them down into charts that let the visitor visualize which expansion and roughly which "tier" the weapon comes from within that expansion pack, and then follows up those charts with excellent descriptions of certain pieces of weaponry. At the end of each post you can find a complete list of the weapons displayed in that post with links to Wowhead that will enable you to track down the drop point for your item of interest, assuming that DE Azeroth hasn't pointed it out earlier in the post. You can find Disenchanting Azeroth on Twitter @deazeroth
Mog-My-Gear - Looking for a bit more of a custom look? Mog-My-Gear just may be able to help! This site already has some pretty neat sets on display, but if they don't have something that you're looking for they invite you to email them with your requests. There's definitely a couple of sets displayed on that site that gets me more than excited for transmog to go live!
WoW Roleplay Gear - Stylize yourself with the help of the gallery over at WoW Roleplay Gear. The galleries on this site are rather extensive and well put together, so definitely give them a look-see. For the latest news and updates on the site, you may follow them on Twitter @WoWRoleplayGear
Revive and Rejuvenate - Angelya over at R&R has now done several posts pertaining to the new transmog features. She's done a few posts to help fellow druids (and potentially rogues) find their perfect gear set(s), breaking things down into tier sets, dungeon and raid sets, pvp sets, crafted leathers (leatherworking), and green quality leathers. She also has a nice little list of folks who have transmog posts/lists that I may not have listed here. You can finder her on Twitter @_angelya
Warcraft Hunter's Union - Looking for hunter tier? Hop on over to your favorite hunter resource site and check out their post on the hunter PvE gear. Fairly basic, but it gets the job done.
Tengen's Blog - Are you a paladin who is at a loss where to find gear to transmog? Tengen's blog is where you can find it. While his collection seems to be a bit of a work in progress, the item sets that are already up are absolutely fantastic. Not only does he display gear sets, but he goes through weaponry, shields, cloaks, tabards, and even mounts that match the different sets as well. Very in depth, incredibly well put together.
Kirina's Closet - While Kirina's Closet doesn't have transmog necessarily in mind, this site has long been around for the WoW RP fashion fan. Kirina has some wonderful RP sets, and I'm sure she has something for you in there somewhere. Check her out on Twitter @kirinascloset
WoW Insider's World of Wardrobe - Another one of Anne Stickney's (Twitter: @shadesogrey) wonderful WoW Insider projects. Once a week she brings you a new post covering various tier sets and set look-a-likes. Get your weekly dose of transmog needs.
WoW:Fashion - A great collection of different gear sets and possible transmogging ideas. This was the site that I actually got the idea (and drop help) for Kelebek's soon to be transmogged set! I just did a few tweaks so that it'd be 100% to my liking, and there you have it! Excellent site, just like all the others.
Blog Celebrities - Would you like to dress up as your favorite blog/twitter celeb? Now you can! Whether you long to look like the PvP master Cynwise (Cynwise's Battlefield Manual/@wowcynwise), the academically minded Perculia (Flavor Text/Wowhead/@Perculia), Loremaster Rades (Orcish Army Knife/@_rades), the raid extrodinaire Vidyala (Manalicious/@_vidyala), or that one silly little disco priest (Disciplinary Action/@discopriest), you may do so by simply following the link at the beginning of the paragraph. Go forth and look epic.
So my dear little hoarders, if you haven't begun your quest to find the perfect outfit for your character(s) before 4.3, may the above resources guide you in your way. Until next week, stay fashionable.