Socialthing! is in private beta - see everything that's going on with your friends in all the sites you use, easily figure out where you're missing connections with your friends, interact with multiple sites at once, and more!
We have taken a sample of nine of these companies - Ning, KickApps, CrowdVine, GoingOn, CollectiveX, Me.com, PeopleAggregator, Haystack, and ONEsite - all of which provide free baseline services, and reviewed them individually below