Activision-Blizzard is holding a game competition where the winner will
receive $100,000. Rather than submit a completed game you need to
submit a two-page summary and a video describing your game idea. There
are NDAs involved, so this doesn't look like another contest where the
corporate sponsor lays claim to all materials submitted.

This looks like a great opportunity, especially if you're working on a
game prototype or at least have a design for a game swimming around in
your head.

Here is the Joystiq article about the contest:
http://www.joystiq.com/2010/02/18/kotick-announces-activisions-half-million-dollar-indie-games-co/

And the initial PDF announcement available on Activision Blizzard's site:
http://www.activision.com/ROOT/media/sweepstakes/indie_game/Indie%20Game%20Competition%20FINAL%20-%20WEB.pdf