Crowds is a project mainly written in RUBY and JAVASCRIPT, it's free.
The code that powers crowdsmachine.com - check site for info
See http://crowdsmachine.com for a demonstration of this code in action.
More info here: http://wp.me/pbkc-8j
Licensed under Creative Commons Attribution-Share Alike 3.0: http://creativecommons.org/licenses/by-sa/3.0/