Amazon is having its 2012 editor's choice sale from now until Dec 31.
Games/packs of games from 25% to 90% off. There are quite a few of 50% and up games. And on top of it all, when you purchase a game, you get a $5 coupon (one time only), making the game even cheaper! I'll be buying Civ 4+expansions, 5+Gods and Kings, and Stronghold for only $15, despite the fact that I already have Civ 4.
http://www.amazon.com/gp/feature.html?ie=UTF8&docId=1000728511
Note: the promotional credit was sent via email from amazon in dec/nov if you purchased a game at that time.
Update: I just purchased it, and I got a promo codes towards AirMech holiday pack and Adventure Quest Amazon Warrior Armor that gets me it for free. So, I'm assuming that will be true for the rest of you.