So you're new to Northrend (i.e. level 68-72) and you want to get lots of Borean Leather (for your leatherworker or for the AH). Problem is most mobs in the starting areas only drop scraps, and it takes 5 scraps to make one piece.
The solution: Kill Great Reef Sharks Creature: Great Reef Shark - Thottbot: World of Warcraft
These guys seem to drop a full piece of Borean Leather (not scraps) every time they are skinned. I only killed them outside of of Valiance Keep but they're in Howling Fjord too and seem to have a pretty good respawn rate.
So grab your skinners, grab some water breathing potions (or use Warlock/Undead/Shaman) and get yourself some Leather![]()