A little change from the usual boasting about my Auction House buying/selling. The new Volatile Air, Volatile Earth, Volatile Fire and Volatile Water have quickly become staples in both the crafting market and in the buying and selling trades. If you want to take a break from the Auction House, here is where you can easily farm these special items, which will sell for a good price.
The most expensive one at the moment is Volatile Air, which you can farm in the Twilight Highlands at The Twilight Breach, an area between Victors Point (alliance) and the Gullet (Horde). They sometimes spawn alone and sometimes are with a caster mob. Both are easy to kill and often drop volatile air, which are selling for enormous profit on the AH.
Volatile Water drop from elementals on the river in Twilight Highlands near the horde and alliance starting towns. They have a good respawn rate.
Volatile Earth can also be farmed from Twilight Highlands near Thundermar and Blood Gulch, and you can also get them from mining.
Volatile Fire is most easiest farmed from the fishing pools that spawn around Ragnaros and Sulphuron Spire in Mount Hyjal. Drop in a fishing cast, and fish up your gold! Easy!
Twilight Highlands is the new Shadowmoon Valley!