If you haven't checked it out by now, you should go straight to your Steam client and see all the crazy deals going on for the Steam Winter Sale. Dungeons of Dredmor for $2.49! That's half price! The expansion pack/DLC for Dungeons of Dredmor, The Realm of the Diggle Gods, is also on sale for only $1.49! This just came out last week! Terraria is also on sale for only $4.99.
These, plus a ton of other awesome games, are on sale with big discounts, so don't miss out. If you have any great deals you want to highlight, leave a note in the comments section.