Through Battle.net or the Blizzard Store you can buy World of Warcraft and The Burning Crusade for just $5 each, and Wrath of the Lich King for $10.
That deal will be running until November 30th, celebrating both the US holiday of Thanksgiving and the upcoming latest expansion Cataclysm.
Launching December 7th, WoW’s Cataclysm will be peddled for $39.99 if you intend to snap up the standard edition. Already the original continents of Azeroth have undergone The Shattering which prepares the MMO for the arrival of the new expansion.