A little background. During the production of Brütal Legend, the publisher (Vivendi) was purchased by Activision who elected not to publish the game. While shopping around for a new publisher (eventually Electronic Arts) the brain wizards at Double Fine decided to tell everybody to stop working on Brütal Legend for two weeks, split into four groups, and develop a game prototype from scratch to be reviewed by the other three groups. This ended up both being a yearly event at DF, and more or less saved the company as EA elected not to publish a Brütal Legend sequel, and Double Fine ended up getting games like Costume Quest, Stacking, Iron Brigade, Once Upon a Monster, Happy Action Theater, and Middle Manager of Justice out of their Amnesia Fortnight prototypes.
So this year, they've decided to let us in on the process. There are 23 pitches at the link above, if you contribute anything financially you will be able to vote for your favorites and the top four will be prototyped, and you will receive Steam keys (Windows only) for the four prototypes.
I would definitely take part, but sadly this is Windows Only.