Nextdoor is a private online social network for your neighborhood. Their mission is “to bring back a sense of community to the neighborhood”. You can research (or add) your own neighborhood by signing up at the Nextdoor site and take a look at their promotional video to see how it works.
Here are some examples of how people are using Nextdoor:
Giving an extra armchair to a neighbor
Getting introduced to a great new babysitter
Organizing a neighborhood barbecue
Learning more about upcoming construction projects
When neighbors start talking, good things happen. Bring back a sense of community to your neighborhood…
via Kevin Rose