The other day I was going through SFK when I noticed our rogue was skinning pretty much everything. I never really thought about it, but SFK is about 95% skinnable NPC's,
If you want to raise your leatherworking from around 75-180's, this is your place. I was able to gather about 10g worth of leathers, and a ton of leveling with my skinning through a couple runs in this place. Not only can you farm it at level 40's, but you can still just run it with some friends and ask to skin. The main drops are light/medium leather, and some hides. Every once in a while you will get a heavy leather.
Note: All the bosses are skinnable except the Captain and Arugal. EVEN Fenrus.
Have fun.