I like Nearbie. Not because it's a particularly outstanding new social network - it's very similar to many social sites built around people, photos and events - but because it creates a new paradigm for thinking about social networks.
Launched officially yesterday, Nearbie allows you and your friends to post events and link them to a place and time. Perhaps you visited Starbucks Fillmore Street in San Francisco yesterday - post about it and share that with your friends and the world. Nearbie creates a "history" of you, your friends and the places that members have visited for the sake of preserving those memories. Obviously there are pages for individual users, places and events, but technically it's not that different to Flickr, or even an events social network like MingleNow or HeyLetsGo.
There's so many social networks out there these days it can be hard to differentiate one from the next. This one sounds interesting with their "timeline" type of linking of events. I'm going to check it out to see if it's any good. If anyone has tried it let me know what you think.