The Barrens is an excellent Horde country to level, mine, and skin, due to the sheer size of the region. It also hosts three instances, which will keep WoW players from level 15 to 40 constantly traveling throughout the region. Most of the monsters in this region consist of lions, striders, and raptors, which will provide the skinner with plenty of leathers--and the ability to level up their skinning with little effort.
A couple of regions in the northern part of this Horde territory are key skinning areas, including the Wailing Caverns instance and some areas around Ratchet, the only neutral settlement in The Barrens.
The Wailing Caverns is not a popular instance for WoW players--most dislike the simplicity of this low level instance--but should be the 
first stop for any serious skinners. Every place in this instance is brimming with Deviate Raptors and elite raptors, which can be skinned for light leathers, hides, and occasionally medium leathers.
The key here is to circle the area before the actual portal inside the instance. Skinners looking to enter the portal should form a group first--sometimes the raptors like to double-team, and two angry elites won't make for happy skinning.
Another bonus is the raptors also drop green items or weapons, which also sell for decent gold on the horde auction house.
Skinning Location: The start of the Wailing Caverns, located just west of Crossroads in The Barrens.
Skinning Mobs: Deviate Raptors at the start of the instance; raptor elites are found inside the portal.
Dangers: The raptors often travel in pairs or groups, and being attacked by multiple monsters is very likely. Other WoW players may also clear the monsters before you even enter the instance. Skinners should visit this area in the night or on weekend, when crowds are smaller.