Sunward Lightbringer (Paladin only)

Lightbringer Faceguard Token to buy this drops from Archimonde in Hjyal Summit or you can buy Vengeful Gladiator's Lamellar Helm from Kezzik the Striker in Area 52 for 1000 Honor Points or get Crown of Empowered Fate from Essence of Anger in the Black Temple.
Lightbringer Pauldrons Token to buy this drops from Mother Sharaz in Black Temple or you can buy Vengeful Gladiator's Lamellar Shoulders from Kezzik the Striker in Area 52 for 750 Honor Points.
Heroes' Redemption Tunic >Drops from Archavon 10 or buy with Chestguard of the Lost Conqueror token that drops from Gluth in Naxx 10 or you can buy it in Dalaran.
Tabard of the Shattered Sun Requires Exalted with Shattered Sun Offensive
Heroes' Redemption Gloves> Drops from Archavon or buy with Gloves of the Lost Conqueror token, which drops from Satharion in the Obsidian Sanctum or you can buy the token in Dalaran.
Tainted Girdle of Mending > Drops from Patchwerk in Naxx 10
Heroes' Redemption Greaves:> Drops from Archavon 10 or buy with token that drops from Thadius in Nax 10.
Sabatons of Deathlike Gloom Drops from Gothik the Harvester in Naxx 10
The Willbreaker Drops from Keli'dan the Breaker in The Blood Furnace heroic
Sunward Crest Requires exalted with Shattered Sun Offensive

Details here.

Quaking Mercury

Got the Dragon-Quake Shoulderguards on a recent trip to Karazhan with my hunter and decided to come up with a transmog set to go with it.

Gurn's Horned Helmet Alliance-only quest reward in Blade's Edge Mountains
Dragon-Quake Shoulderguards Drops from the Curator in Karazhan
Haurberk of Totemic Rage Blue BOE
Tracker's Belt Drops from Mennu the Betrayor in the Slave Pens
Scalewing Gloves Alliance-only quest reward in Blade's Edge Mountains
Searingscale Leggings Drops from Pyromancer Loregrain in Blackrock Depths
Bloodshot Greaves Drops from the Shade of Hakkar in Sunken Temple
Striker's Mark Drops from Magmadar in Molten Core
Sha'tari Anchorite's Robe Quest reward in Outlands

Most of the pieces in this set are look-alikes of the green BOE Mercurial Mail set.

Details here.

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

Corrupted Mooncloth

Vengeful Gladiator's Mooncloth Hood Priest-only PvP reward.
Merciless Gladiator's Mooncloth Mantle Priest-only PvP reward.  The token to buy it drops from Void Weaver in The Eye.  ** Update 11/22/2013:  Not sure when this changed, but you can now buy this from Kezzik the Striker in Area 52 in Netherstorm for 750 Honor.  **
Raiments of the Corrupted Drops in Ulduar 10
Binding of the Dragon Matriarch Drops in Ulduar 10
Pulsar Gloves Drops in Ulduar 10
Royal Boots Green BOE
Tower of the Mouldering Corpse Drops in the Forge of Souls
Deathchill Cloak Made by Tailors.  There are a few other cloaks with the same appearance.

Details here.

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.

Changes to Scholomance in Mists of Pandaria

Be aware that with the release of Mists of Pandaria, there will be major changes to Scholomance, including elimination of the four minibosses before Darkmaster Gandling.  These minibosses drop pieces of the following sets, which presumably will no longer be available.

http://www.wowpedia.org/Scholomance_(Mists_of_Pandaria)

Necropile Raiment

Cadaverous Garb

Bloodmail Regalia

Deathbone Guardian