Wait 3 months.
Then look mainly at things that say they support oStatus.
What is oStatus?
oStatus is emerging as the main protocol that will support distributed social networking.
It's a collection of other technologies that enable the distributed social web.
- webfinger - for finding friends, openid, service discovery etc.
- salmon protocol - for making sure comments on one site flow to back upstream to their originators.
- PubSubHubBub - a webhook protocol for distributing messages.
- ActivityStreams - an extension to RSS/Atom to represent things like "Bob published this photo"
- PortableContacts - Secure address books and friends list.
You seem like someone who will want distributed social networking as it let's the marketplace combat the lock-in power of the network effect Facebook has. Right now, it's hard to leave Facebook because everyone is on it. Once the dam bursts with oStatus, it will be much easier to leave any social networking site without leaving your social network. This sets up a marketplace and ecology where sites will compete on features, security, and privacy for your membership - but they don't get to hold you hostage.
Where is it?
There is a bunch of stuff happening in the open social web right now.
Wordpress is getting an oStatus plugin/aggregator called SocialRiver. They are in alpha/development right now. In the meantime there are already wordpress plugins for most of the oStatus spec.
6D has code on github right now and some demo sites. They were going to use xmpp but I believe from the mailing list that they will support oStatus.
Status.net, the folks who made identi.ca are leading a lot of the charge on oStatus and are supporting it right now.
Elgg, an open source social network, has started down the ostatus road by adding salmon, and they are working on the rest.
The root cause of our discontent with most social networks - be they myspace or facebook or orkut or whatever, is the power differential. If facebook or myspace decide to do something you don't like, you can't leave because your social network is locked into that site. Making the whole thing distributed means you can change your provider - just like you can change your ISP or email provider.