This piece from Bloomberg BusinessWeek describes the effort to get Diaspora, a new social network (open source by my interpretation) off the ground.
I joined Diaspora several months ago. I am a little frustrated because the service seems to have little activity relevant to my interests, but I suppose that is the way it goes with startups. Someone has to generate some content so that others find the site useful, etc.
What I find interesting is that Diaspora offers code such that one could set up their own site. The present install process is a bit beyond my pay grade (unless I really wanted to take some time), I am thinking providers will eventually offer install scripts should you want to host a site yourself.
Diaspora is offering invites if you want to take a look.