Pleroma - Pleroma is a free, federated social networking server built on open protocols.
ZeroMe - Social network for the distributed P2P network ZeroNet.
GNU social - GNU social is communication software for both public and private communications.
Identi.ca - Social & Communications
ColdCast - An open social network with zero corporate interference.
Scuttlebutt - A decent(ralised) secure gossip platform.