The population of World of Warcraft is surging thanks to the release of the Cataclysm expansion this week. To prevent over-crowding on some servers, Blizzard is offering free character moves.
"Please be aware that due to the unpredictable nature of free transfers we may close down any Free Character Moves at any time and without warning if the target realm becomes full," said Blizzard. "If you plan to move with friends or your guild, we suggest that you coordinate the effort to reduce the chance of any stragglers being left behind."
If you want to take advantage of the free transfers listed below, you should do it soon. They're only being offered until December 22nd. The official FAQ explains the finer details of the process.