In addition to GOG's amazing holiday sale, Steam has shown its Christmas spirit with up to 80% off hundreds of games. Some noteworthy deals include 50% off Ubisoft and THQ's entire catalog as well as the Eidos Collector's Pack, 66% off all Atari games and the Unreal pack, and 33% off 2K titles and the Rockstar Collection.
Along with the "standard" discounts, Steam is hosting daily special deals, marking down popular titles like GTA IV ($7.49), Defense Grid ($2.49), S.T.A.L.K.E.R.: Shadow of Chernobyl ($1.99), Operation Flashpoint: Dragon Rising ($19.99), and Mirror's Edge ($4.99). When these expire in 22 hours or so, another selection of hits will take their place.
The event will end on January 3, so there's plenty of time to take advantage of the savings. If you spot something that's simply too good to pass up, tell us about it in the comments.