You'll find them at networkedneighbourhoods.com.
I've only gotten to the summary (PDF), but the general thrust is this: "The research shows that they serve to enhance the sense of belonging, democratic influence, neighbourliness and involvement in their area. Participants claim more positive attitudes towards public agencies where representatives of those agencies are engaging online."
Among other things:
- 42% of those surveyed said they met someone in their neighborhood online
- 75% said participation on the sites made it more likely people would pull together to improve their neighborhoods
- 69% felt a greater sense of belonging
- From a quarter to about two-thirds (depending on the site) said people make negative remarks online, but three-quarters said they are quickly countered.
But this looks to be useful reading and a block on which to build further research.
[Also posted on Common Sense Journalism]