This is fresh off the top of my head, I haven't even used this yet but Diaspora is an open source social networking site that is being released slowly now and seems to be gaining some momentum. They have an entire page explaining how anyone in the world can run Diaspora off their own host and be their own 'pod' (their words).
I thought this might have massive potential in creating a social networking 'pod' devoted to the Occupy Movement worldwide - open source, non-corporate, no ads, no ownership (i.e. Diaspora won't own the content you post), created by four NYU nerds angry about Facebook's privacy controls. They made a kickstarter to raise $10,000 and accidentally raised $100,000 - oops.
I am a graphic designer and don't even understand half of the words in the instructions on setting this up, but it seems - at the first glance of a total novice - to be really promising. Does anyone want to look into it further? See what potential it holds? Maybe even contact them directly? They seem like the right kind of guys who are probably already personal supporters of the movement (although I bet they rarely leave their rooms).
Instruction for hosting a pod: