Mists of Pandaria queues got you down? Our sister site sussed out the fact that Blizzard is offering free time-limited realm transfers for some North American World of Warcraft servers. If you're on one of eight high-population realms, you can migrate immediately (though you can't choose your destination shard).
Blizzard says that guilds may also move as long as the leader purchases a Guild Master Realm Transfer, after which point the remaining member migrations will be free of charge. Head to WoW Insider for full details.