Diaspora - The online social world where you are in control.
BuddyPress - WordPress social networking in a box.
Friendica - Decentralisation - Privacy - Interoperability
PeepSo - PeepSo is a FREE WordPress plugin which allows you to easily create gorgeous user profiles and spectacular communities within your WordPress site.
Facebook - Connect with friends, family and other people you know. Share photos and videos, send messages and get updates.
Ultimate Member - The easiest way to create powerful online communities and beautiful user profiles with WordPress.