I know that this place has been talked about for ages and ages, and there's a million posts about the place, but after blizzard changed the way the area worked, I feel like it's worth rementioning.
Oronok's farm in SMV. Coordinates: 53, 23
This place used to be (and I guess, still could be) an incredible place to grind. The farm consists of Boars that respawn rapidly. Until the last patch, they dropped vendor trash, and the farmer, Oronok, is a vendor (who also can repair).
With 2.4 (I think), blizzard got rid of the boar's loot tables.
The cool thing is, they're still skinable, and 90% of the time they skin a knothide leather.
In 30 minutes, I've gathered 5 STACKS of knothide leather and 4 STACKS of knothide leather scraps.
And for those who don't know, the best part about the farmer is that he will HEAL YOU whenever you fall below 50%. His heals hit for around 3.3k
Again, I know this place has been talked about a million times, but this is to let skinners who didn't think of the place know about it.