Want to make some coin in a lucrative new market? Flipping Transmog items might just be for you. The first port of call I highly recommend is Disenchanting Azeroth where Keelhaul gives you an enormous amount of information about the market, as well as some stunning graphics that bring your transmog options to life. The second thing to do is follow @DEazeroth on twitter, since that's where Keelhaul is most active these days.
Lastly, if you want to dive into searching for bargains and begin the flipping, head over to the Hatchery at Power World: Gold, where Jim has hosted Keel's unabridged lists for Cloth, Mail and Plate armor, as well as a host of other information.
So credit where credit is due, these lists are NOT mine, they are Keel's... I've just done the translation into Auctionator shopping lists for use by the gold making community. I highly recommend reading Keel's post for each type of armor, so you get an understanding of his theory about where particular sets should be priced. I've also stopped with each list at the threshold recommended by Keel for low population or poor transmog market servers.
I haven't personally done a great deal with Transmogrification for profit, but the little I have has been very rewarding. Turning a green quality helm from a 20g purchase into a 700g+ sale to double your working capital as a new character on a new realm is pretty damn exciting, so have a play with it and make coin!
Alto has a guide to importing Auctionator shopping lists if you need assistance getting these lists up and running. Grab his weapons list while you're there too!
Plate - The Unabridged Mogging Plate Flip List by Keelhaul
*** transmog_plate Armor/Plate/Alabaster Armor/Plate/Bloodfist Armor/Plate/Commander Armor/Plate/Jade Armor/Plate/Bloodscale Armor/Plate/Boulderfist Armor/Plate/Brutish Armor/Plate/Darkcrest Armor/Plate/Exalted Armor/Plate/Glorious Armor/Plate/Hyperion Armor/Plate/Imbued Plate Armor/Plate/Lofty Armor/Plate/Overlord Armor/Plate/Saltstone Armor/Plate/Tyrant Armor/Plate/Vanguard Armor/Plate/Warleader Armor/Plate/Warlord's Armor/Plate/Warmaul
Mail - The Unabridged Mogging Mail Flip List by Keelhaul
*** transmog_mail Armor/Mail/Glimmering Armor/Mail/Battleforge Armor/Mail/Chief Brigadier Armor/Mail/Blood Knight Armor/Mail/Captain Armor/Mail/Combat Armor/Mail/Masterwork Armor/Mail/Engraved Armor/Mail/Lord’s Armor/Mail/Hero’s Armor/Mail/Ornate Armor/Mail/Steadfast Armor/Mail/Sentry Armor/Mail/Wrathfin Armor/Mail/Radiant Armor/Mail/Black Dragon Mail Armor/Mail/Magnificent Armor/Mail/Triumphant Armor/Mail/Knight’s Armor/Mail/Sparkleshell Armor/Mail/Ancient Armor/Mail/Blackforge Armor/Mail/Protector Armor/Mail/Brigade Armor/Mail/Ebonhold
Cloth - The Unabridged Cloth Mogging Flip List by Keelhaul
*** transmog_cloth Armor/Cloth/Silksand Armor/Cloth/Vital Armor/Cloth/Vicious Embersilk Armor/Cloth/Felcloth Armor/Cloth/Mooncloth Armor/Cloth/Elegant Armor/Cloth/Nightsky Armor/Cloth/Lunar Armor/Cloth/Sage Armor/Cloth/Windchanneller's Tunic Armor/Cloth/Windchanneller's Leggings Armor/Cloth/Beaded Armor/Cloth/Ancestral Armor/Cloth/Aboriginal Armor/Cloth/Barbaric Cloth Armor/Cloth/Mystic Armor/Cloth/Hibernal Armor/Cloth/Silver-Thread Armor/Cloth/Black Velvet Robes Armor/Cloth/Stonecloth Armor/Cloth/Highborne Armor/Cloth/Gaea Armor/Cloth/Imperial Red Armor/Cloth/Councillor's Armor/Cloth/Regal Armor/Cloth/Mystical Armor/Cloth/High Councillor's