Well, basically there's five pretty darn solid/fun games for whatever you want to pay - not that you should necessarily aim low, as two thirds of the final money goes to charity!
It includes Gish, Lugaru, Aquaria, World of Goo and Penumbra Overture... which are all really good! (Note: I've not played Lugaru or Aquaria, but I'm told they're good. Anyone got an opinion?)
Anyway, I'll pass you over to RPS, where I found this: