I found meetup.com is a pretty good place for this, depending on where you are. It's a bunch of people looking for some kind of communal group based on shared interests (programming, political philosophy, SciFi, religion, learning Italian, hiking, etc.). Of course you have to find the right group that fits you, but when you do it's great.

Other places I've had success is with local political/activist groups and hobby groups (dance groups, martial arts groups). Again, you have to try a lot of groups to find the right one, but it's worth it.