Blizzard has reopened character transfers on select realms. This is done to help allieviate some of the more overpopulated servers that at many times, especially during peak hours, have queues of a half hour or more!
Blizzard has listed the realms that are avalible now, along with a list of soon to come:
Blackrock → Bloodscalp
Icecrown → Azjol-Nerub
Deathwing → Stormscale
Those will be open for approximatly two weeks so act fast if you're planning on transfering with a group of friends or guild.
Also planned for server moves in the future are:
Frostwolf → Frostmane
Ner'zhul → Crushridge
Proudmoore → Dragonblight
Silvermoon → Draenor
Archimonde → Firetree
Kil'Jaeden → Boulderfist
Tichondrius → Dunemaul
Doomhammer → Perenolde
Good luck to those who transfer their characters, and have fun on a different server!
Links
Blizzard Entertainment - Source
Blizzard Entertainment - Move A Character