Looks like Blizzard is going to allow folks on 5 different servers to transfer for free to another realm. The catch? The destination realm is not up for discussion. If you are on Bronzebeard, you are getting a free transfer to Hyjal, and you better like it! I am assuming Blizzard did their research and the source realms are overcrowded and the destination realms could use some more players, but I don't have any first hand experience on these servers, so hey, this could be the worst thing ever. But I doubt it.
For those of you behind firewalls at work, here are the free transfer realms...
Bronzebeard to Hyjal
Aggramar to Kael'thas
Alexstrasza to Muradin
Thrall to Norgannon
Gnomeregan to Kilrogg
Finally, these transfers will be available until December 7th, but Blizzard will close transfers early if they see an adequate number of players moving, so get in while the getting is good.