Meetupedia - Looks nice. Easy Facebook registration. Hard to find groups in your area due to no location search.
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
DownToMeet - DownToMeet is a platform to organize, find, and attend group events.
Mighty Networks - Mighty Networks enables entrepreneurs, organizations, and companies to create and grow a community-powered brand.
lclz.in - Have you ever wondered where your friend are ?