Felcloth

Unlike other cloth items, Felcloth drops from demons instead of humanoids. Felcloth can also be purified to make Mooncloth.

Source
Prior to Patch 4.0.3a, Felcloth dropped off demons in Azshara, Blasted Lands, Dire Maul, Felwood, and Winterspring.

Leatherworking

 * Wicked Leather Armor

Tailoring

 * Mooncloth
 * Core Felcloth Bag
 * Felcloth Bag
 * Felcloth Boots
 * Felcloth Gloves
 * Felcloth Hood
 * Felcloth Pants
 * Felcloth Robe
 * Felcloth Shoulders
 * Robe of Winter Night
 * Robe of the Void
 * Runed Stygian Belt
 * Runed Stygian Boots
 * Runed Stygian Leggings

Places to farm

 * Lvl. 50+: Felwood, just west and north west of Jadefire Run located in the North part of Felwood. (Runecloth also drops here.)
 * Lvl. 50+: From the Felguards (surrounding the Dark Portal) in Blasted Lands.
 * Lvl. 52+: From the Satyrs (Legash Encampment) in Azshara.