A site in india, jaagore.com(means wakeup), allows people to volunteer for a good social cause, or start a movement themselves. I think this domain could be helpful for similar site. You can also make use of Facebook/Twitter api to bring the social element into it.

Another use that comes to my mind is to use this domain to power a review site, may be a community powered startup review site where hackers, designers and entrepreneurs can review startups and provide suggestions for improvement. Think over this. If successful, it can turn into a good place for budding entrepreneurs to look for relevant information.

A platform for people to submit ways to improve the current state of anything they think is sub par, like a school curriculum, bad traffic intersection, poor park maintenance, etc. it could show you suggested improvements near to you, and people could upvote ideas they believe in. empowered people could see what the community wants and volunteer time towards improvements, or some could be used as petitions for local govt, schoolboards, etc