Transcendent Lightling

Finally finished my transmog set built around Robes of the Exalted.

Aurora of Transcendence Dropped in Blackwing Lair.  Priest only.
Lightning Infused Mantle Quest reward from Halls of Lightning.  Don't despair if you did this quest when WOTLK first came out and then vendored these shoulders.  The WOTLK dungeon quests have been reset and the quest giver is now inside the entrance of the dungeon.
Robes of the Exalted Drops from Lord Aurius Rivendare in StratholmeRuned Spell-Cuffs Bought for Justice Points in ShattrathFrostweave Gloves Crafted by tailors
Hammer of the Astral Plane Drops from Kel'thuzad in Naxx 10
Igniter Rod Drops from Ignis in Ulduar 10
Dawnspire Cord Drops in Sunken Temple

Sun-Infused Sin'dorei

Circlet of Prophecy Priest Tier 1.  There are lookalikes--check Wowhead.
Flarecore Mantle Made by tailors.  Requires Thorium Brotherhood rep to buy the pattern.
Scarlet Sin'dorei Robes Drops in heroic Magister's Terrace.
Girdle of Ruination Made by tailors.  Pattern is a world drop.
Imperial Red Gloves Green BOE
Imperial Red Boots Green BOE
Perdition's Blade Drops in Molten Core.
Flametongue Seal Bought for Justice Points in Shattrath.

Alternate versions

Whitemend Hood Made by tailors.
Primal Mooncloth Shoulders Made by tailors.
Girdle of Prophecy Priest Tier 1
Sun-Infused Focus Staff Drops in Magister's Terrace.  The green BOE Frenzied Staff is another Blood Elf style staff.

Red Linen Sash Alliance only quest reward in Elwynn Forest.
Mantle of the Corrupted Drops in Naxx 25.
Lok'amir il Romathis Drops in Blackwing Lair.

All details here.

Hero's Acumen

Unfortunately, the Robes of Acumen are no longer obtainable.  I still have mine from a Maraudon run way back in Vanilla WOW.

Heroes' Shoulderpads of Faith Priest Tier 7.  Token Spaulders of the Lost Conqueror drops in Naxx 10.

Acumen Robes No longer available.  Used to be a quest reward from Maraudon.

Chillbane Belt Drops in Hour of Twilight.

Resplendent Bracelets Green BOE

Mystical Gloves Green BOE

Kurkenstoks Alliance-only quest reward on Azuremyst Isle.

Surgeon's Needle Dagger drops in heroic Pit of Saron.

Manual of the Nethermancer Drops in The Mechanar.  (Book of Blood and Stormbound Tome--both made by incription--have the same appearance.)

Alternate versions

Runecloth Shoulders Made by Tailors

Rod of the Sun King Mace drops in The Eye

Staff of Dominance Staff drops in Molten Core

All details here.

Icy Mooncloth

Here's a set based around the Mooncloth Robes for a Frost Mage or healy Priest.

Royal Headband Green BOE
Regal Mantle Green BOE
Mooncloth Robe Made by tailors
Ebonweave Gloves Made by tailors.  They are long enough that most bracers shouldn't show.
Mindfire Waistband Drops in the Blood Furnace
Staff of the Unknown Road Quest reward from Zul'Farrak
Regal Boots Green BOE

Alternate version

Underworld Mantle Drops in Ulduar 10 normal
Grand Magister's Staff of Torrents Drops in Sunwell Plateau

Alternate Shoulders

Khadgar's Shoulderpads of Triumph Alliance Mage Tier 9

Merciless Gladiator's Mooncloth Mantle Priest-only PvP reward.  The token to buy this drops from Void Reaver in the Eye.

Sanctified Crimson Acolyte Mantle Priest Tier 10

All details here.

Fire! Fire! Burning! Burning!

Put this set of mostly crafted items together for your favorite fire mage.

Elegant Circlet Green BOE

Cindercloth Robe Made by tailors

Red Mageweave Shoulders Made by tailors

Red Mageweave Gloves Made by tailors

Red Linen Sash Alliance-only quest reward from Elwynn Forest

Rod of the Blazing Light Drops in Heroic Magister's Terrace

Resplendent Cloak Green BOE

Details here.

Update 8/17/12:  added screenshots.

Draenic Wind Serpent

Ever wish your clothie looked like a druid?  Now you can with this transmog set built around Embrace of the Wind Serpent, an epic drop from the Sunken Temple.  The inspiration for this set actually was the bracers, the Goldenvine Wraps, that I got as a quest reward when I was farming the Slave Pens for something else.

Conjurer's Hood Green BOE.  There are several other BOE's you could substitute here--check the Wowhead link.
Embrace of the Wind Serpent Drops in the Sunken Temple off the Shade of Hakkar.  Very low drop rate--expect to spend a lot of time farming that robe.
Ivycloth Mantle Green BOE
Feralfen Sash Green BOE
Goldenvine Wraps Quest reward from the Slave Pens.  Don't worry if you completed this quest when Burning Crusade was new and no longer have the bracers.  The quest has been reset and the quest giver is now at the dungeon entrance.
Heavy Linen Gloves Crafted by tailors.
Vinerot Sandals Drops in Maraudon
Draenic Wildstaff Drops in Auchenai Crypts.  This staff has a eye-catcing blooming flower animation.  There is a druid-specific quest reward with the same model.

Details here.

Alternate version using pieces from the green BOE Mistyreed set.

Mistyreed Shoulderpads
Mistyreed Bracers  This has the same model as the Goldenvine Wraps, but in a different coloration.
Mistyreed Gloves
Mistyreed Belt  Chloromesh Girdle (drop from Maraudon) has the same model and coloring.


Details here.

Primal Mooncloth Dragon Slayer

Combines pieces from the Primal Mooncloth set and a low-level Alliance quest reward.

Whitemend Hood Crafted by tailors
Primal Mooncloth Shoulders Crafted by tailors
Robe of the Dragon Slayer Quest reward from Alliance only quest on Bloodmyst Isle
Primal Mooncloth Belt Crafted by tailors
Sterile Flesh-Handling Gloves Requires Knights of the Ebon Blade reputation to purchase
Ethereal Boots of the Skystrider Drops in normal mode Mana Tombs
Gavel of Pure Light Requires Sha'tar reputation to purchase.  There are several other maces with the same appearance--check the Wowhead link.
Swamplight Lantern Drops in heroic Slave Pens


Details here

Update 6/23/12:

Got tired of farming heroic Slave Pens for the Swamplight Lantern, got even more tired of farming Arcatraz for a slightly different color of the same model, and I didn't feel like spending my Justice Points on Hermit's Lamp.  I lucked out and found Dreamseeker Dandelion for sale at the Auction House, so I went with that for my offhand.

Update 8/17/12:

Alternate weapon:  Redemption.  Drops in what we used to call Live Strat.

Exalted Lightning

Based around Robes of the Exalted from Stratholme and Lightning Infused Mantle.

Aurora of Transcendence Dropped in Blackwing Lair
Lightning Infused Mantle Quest reward from Halls of Lightning.  Don't despair if you did this quest and  when WOTLK first came out and then vendored these shoulders.  The WOTLK dungeon quests have been reset and the quest giver is now inside the entrance of the dungeon.
Robes of the Exalted Drops from Lord Aurius Rivendare in Stratholme
Runed Spell-Cuffs Bought for Justice Points in Shattrath
Frostweave Gloves Crafted by tailors
Nethershard Girdle Dropped by Moroes in Karazhan
Slippers of Serenity Dropped by Exarch Maladaar in Auchenai Crypts
War Mace of Unrequited Love Dropped by Keristrasza in heroic The Nexus
Swamplight Lantern Dropped by Quagmirran in heroic Slave Pens

Details here

Alternate version #1.  You'll have to find some pants that don't show too much.

Robes of the Guardian Saint Drop from Temple of Ahn'Quiraj
Dawnspire Cord Drops in the Sunken Temple

Details here

Alternate version #2, using Replica Virtuous Crown as well as the replicas of the bracers, gloves, and belt from the Vestments of the Virtuous set.

Details here

Versions by other people here.

Ruthless Pigment

Based on the Kalu'ak Pigment-Stained Robes.  The helmet is priest-only.

Details here

Ruthless Gladiator's Mooncloth Helm Priest-only PVP
Fel-Tinged Mantle Drops from Vexallus in Magister's Terrace
Pigment-Stained Robes Kalu'ak rep gear
Nethershard Girdle Drops from Moroes in Karazkan
Moonshroud Gloves Crafted by tailors
Ethereal Boots of the Skystrider Drops from Nexus-Prince Shaffar in the Mana Tombs

Duskwoven Sylvan Wraps

A muted seafoam green set made up of drops from Vanilla WOW instances mixed with pieces from the green BOE Duskwoven set.

Details here

Coldtouch Phantom Wraps Drop from Baroness Anastari in Stratholme.  Same appearance as the Duskwoven Robes, but with longer sleeves.
Burial Shawl (drop from Scholomance) / Duskwoven Amice
Sylvan Crown Made by tailors.  Requires Cenarion Circle reputation to learn.
Shimmering Sash Low level green BOE.

Edit 6/22/12:  Added another screenshot.