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