The free character migration to allow players on Molten Core, Shadowmoon, Stonemaul and Warsong to join larger realm communities has been opened. The destination realms for each are the following:
Molten Core –> Burning Steppes, Deathwing, Dentarg
Shadowmoon –> Boulderfist, Spinebreaker, Xavius
Stonemaul –> Ahn’Qiraj, Burning Blade, Jaedenar
Warsong –> Auchindoun, Bladefist, Haomarush
For more information about this migration, please read this thread.