I'm a local organizer, so anyone in the Cincinnati area, please sign up for ours. We have some great facilities at Miami University and good sponsors. Here's the usual info:

Game Jam participants range from amateurs to professionals and include industry professionals, students, faculty, hobbyists and anyone with a passion for making games. In its second year, the GGJ is a global experiment in creativity you won’t want to miss.
The Miami University location offers a beautiful campus with state of the art computer labs, supportive staff and faculty, and easy access to everything you would need to make your game Jam weekend an unforgettable experience.
What is a Game Jam?
ParticipantsAs the folks at the Toronto Game Jam put it – a game jam is an around the clock, game making binge. Coders, artists, musicians, designers and people who love game making join forces to bless the world with a new computer game. They work intensely over a weekend, and share a passion for games.
A game jam is also an unforgettable bonding experience. A full weekend of hard work, a crazy deadline, and the kind of creative inspiration that only comes at 2:00 am. Think pizza, white boards, Mountain Dew, and aha moments.
- http://www.GlobalGameJam.org: The official site
- http://aims.muohio.edu/gamejam:Our Local Jam