Factional mounts: Apprentice
These mounts give a 60% speed increase on land. You can purchase these mounts from <Kennel Master> in the Valley of Honor in Orgrimmar so long as your character has riding skill of 75 (obtainable at level 20). If you are playing as any race other than an orc, you will also need to have Exalted reputation with Orgrimmar.
Factional mounts: Journeyman
These mounts give a 100% speed increase on land. You can purchase these mounts from <Kennel Master> so long as your character has riding skill of 150 (obtainable at level 40), and are restricted similarly to the apprentice mounts above.
Other Wolf mounts
The Black War Wolf is available from <Mount Quartermaster> in Orgrimmar for marks of honor from Alterac Valley, Arathi Basin, and Warsong Gulch. You do not need to have exalted reputation with the Darkspear Trolls to purchase it.
Wolf mounts as loot
The Swift Horde Wolf is a loot item from a successful 10 man Trial of the Crusader raid by a Horde party.
These used the old Wolf mounts graphics, and can be exchanged for the newer variety if desired.