According to worldofwar.net there are a couple for the Horde:
Krulmoo Fullmoon, 42, Camp Taurajo, Barrens
Narv Hidecrafter, 42, Ghostwalker Post, Desolace
Karolek, 35, The Drag, Orgrimmar
Brawn, 35, Grom'gol Base Camp, Stranglethorn Vale
Tarn, 36, Elevation 2, Thunder Bluff
Arthur Moore, 35, Rogues' Quarter, Undercity
These are listed as expert leatherworkers that can train you to journeyman.
Here is the Artisan Leatherworker:
Una, 46, Elevation 2, Thunder Bluff
She(?) can train you to Expert.
And finally:
Hahrana Ironhide, 55, Camp Mojache, Feralas
He(?) can train you to Artisan.
As I have not played a Horde Leatherworker yet, I can only regurgitate information that others have compiled. I hope this helps.