Crossed Paths is a free mutliplayer improvisational storytelling game that I developed. It has players working together to create original stories, and works well for at least 5 players with no limit to the maxiumum number of players (I have run Crossed Paths for a room full of 400 people).
It is a good fit for libraries, schools, churches, or any organization with the goal of having participants explore characters, settings, and conflics from stories they already know.
This game is released under Creative Commons, with the expectation that the facilitator will fill out a short survey about the game afterwards. Crossed Paths is freely available at http://tinyurl.com/crossedpaths