Circle Rules is a fast-paced, chaotic and inclusive alternative sport that combines a huge bouncy ball with a single goal and very few rules. Be ready for a combination of running, jumping, kicking and throwing in a friendly and relatively non-competitive setting.
Some photos of the last game: http://www.flickr.com/photos/45680441@N02/sets/72157629455860684/
You can read more about Circle Rules here: http://circlerulesfederation.com/