I received an email from Photojojo today that describes a really neat participatory global photo project called Inside Out:http://www.insideoutproject.net/. It's the brainchild of a TED prize winner, the artist known as JR.
I think the object is to create a self-portrait, upload it to their site and you then receive a poster of it. Then you take a picture of yourself with the poster. Individuals can do this, but there's also the opportunity for groups to create their own project around this concept: http://www.insideoutproject.net/docs/group_action_guide.pdf
Hope you'll check it out!