Holy crap indeed. Left for Dead 2 is on sale right now for the next 20 hours, for $10. That's right, $10.20 for the game on Steam. That's 1/3rd the price that I paid for my copy.
Audiosurf is $2.50 right now, which is a pretty good deal if you feel like playing a mediocre guitar hero racing knockoff. (that's right)
As well as Star Wars: The Force Unleashed being $7.49. I've never played it, but I've heard good things.
Check out the front page for the rest of the deals.