I've been working on Mobtropolis for about 10-12 weeks now. It's was finally released last week Tuesday. It's something that makes people expand their world by helping them discover and share local adventures around them. The easiest way to think about it is as a dynamic large-scale photo scavenger hunt or a photo-dare site that helps you expand your world--hopefully for the better.
Behavior is hard to change, so it's framed slightly in terms of a game. The basic mechanics should be familiar to those that frequent social news sites. Anyone can submit scenes or vote them up. The higher something's voted, the higher its visibility to others. Anyone can do a scene and take a photo as proof. They can then send it in via their camera phone, or upload it from their digital camera when they get back to desktop. Their friends who voted for a scene will then get an email with the photo attached.
It's been oddly thrilling to get photos of people doing scenes that you submitted.
There's still a lot of work to be done on it. Eventually, I hope to marry the virtual and the real in a tighter loop and better integration with mobile devices. However I'm putting it out in according to startup mantras of "Release early, then iterate like crazy". So check it out, and if you'd be so kind, give me some feedback, good or bad, so I can make it better.