A location-based social network that connects directly to Twitter. You can share your location and also locate friends geographically from the web or your mobile phone. The service also offers an easy and direct channel for uploading pictures and notes to BrightKite and also Twitter. It's perfect for those with camera phones!
Brightkite has an excellent interface and does an admirable job of locating businesses. I think its basic location functions are vastly superior to Foursquare but my social network is not centrally located and the overhead of checking in at new locations has not resulted in any significant benefits for me.