OLPC is hosting a Physics Game Jam in Boston from August 29 to 31.
This is a team based rapid game development competition based on creating a physics game for OLPC XO laptops in 48 hours. Remote entries are allowed, and there will be prizes for the winners. PyBox2D is the main physics library that will be used, but anything open source that will run on the XO is fine.
There will be programming workshops such as developing in Sugar, using PyBox2D, and integrating computer vision with physics, so prior experience is not a requirement.
There is more information on the OLPC Wiki: http://wiki.laptop.org/go/Physics_Jam
Registration is free, but donations are encouraged: http://olpcphysics.eventbrite.com/