Friendica is an open source, free social web server running on the popular LAMP stack.
Think WordPress or Drupal, but for social. It is a mature platform with over two years of development behind it, and provides a wide range of connectors to both legacy and indie social networks.
Your "friends" can be from Diaspora, Twitter, StatusNet, pump.io, weblogs and RSS feeds - and even email.
No other project has ever brought together the social universe into a single federated stream to this degree. It has pioneered ground-breaking technology such as decentralised photo albums with working privacy controls and cross-site wall-to-wall posting via hidden single sign-on.
Not even Facebook will protect your private photos from "fuskers" (look it up, but be warned - it's real creepy). Make a Friendica photo private, it's private.
Caveat: Some of the corporate-owned networks are not happy that Friendica has managed to integrate their networks so seamlessly and have started to close off and restrict the ability to interact with their members. Friendica can stand on its own, while it lasts, it is pleasant to interact in a global social space that has no walls.