The Python Game Programming Challenge http://pyweek.org/ will run its 17th challenge during the first week of September, from the 1st to the 8th.
The PyWeek challenge:
1. Invites entrants to write a game in one week from scratch either as an individual or in a team, 2. Is intended to be challenging and fun, 3. Will increase the public body of game tools, code and expertise, 4. Will let a lot of people actually finish a game, and 5. May inspire new projects (with ready made teams!)
Check out the help page for how to compete (and prepare) and the growing resources message board post: