I made this Fel Hide farming guide to help out players who want to farm the leathers instead of buying them from the Auction House.
There were no major changes to Fel Hide drop rates, so this guide can be used for Burning Crusade Classic (TBC) and Retail WoW. But, if you play Retail WoW, you should learn Outland Skinning from Seymour in Shattrath City before they start farming, or you will get fewer leathers.
The best place to farm Fel Hide is Arklon Ruins in Netherstorm. Artifact Seekers have the highest chance to drop Fel Hide, and they respawn quickly.
You can also farm Warp Chasers around Manaforge Duro. They have the same drop rate as the Artifact Seekers and also respawn quickly. The only downside is that they can go invisibly, which can be a bit annoying.