Pay "whatever you feel like" and get;
Superbrothers: Sword & Sworcery EP
Amnesia: The Dark Descent
Pay more than the average (Currently US$8.34) and also get:
Super Meat Boy
All are available for Mac, Linux and PC, and either as DRM-free direct downloads, BitTorrents, or Steam.
Part of the purchase goes to the author, part to the Humble Bundle people, and part to the EFF and/or Childs play charities.
Worth the price of admission just for Psychonauts IMO.