Another game that I've gotten addicted to recently is World of Goo, which is an award-winning puzzle game from last year. Last year I really liked the demo of the game, but just couldn't justify paying the USD$20 they were wanting for it.
Well right now they're celebrating the first birthday of the game, and the awesome independent developers (2D-Boy) are running a special this week in which you can pay whatever you feel like and get the game. Yep, pay anything you like for it; from a single US cent to whatever. Big props to 2D-Boy for this, and as well as having no DRM in the game too.
I bought the game for $5, because for me that's what it's worth to me without being a tightarse. Unfortunately, not a lot of people are the same as me, and this article from Kotaku reveals that the majority of people are only putting in the bare minimum, which is really disappointing, but not at all surprising.
Nevertheless, I really recommend you get this game. It's fun to play, gets your mind thinking, and pulls a lot of surprises. But please, be decent people and pay more than a couple of cents for it; awesome well-executed ideas deserve a bit of reward.