A decentralised social network implemented over telepathy tubes (that is, currently, GTalk, Jabber and XMPP) rather than via the web.

To install, probably easiest to use my PPA by adding ppa:sabik/connectr to your Software Sources and then installing "connectr" via synaptic; however, do note that in addition to connectr, this may also upgrade your version of telepathy-gabble to the bleeding edge (connectr will not work with the version of telepathy-gabble that's in karmic or lucid).