Friendica

Friendica is a distributed social network application which runs on commodity hosting platforms - PHP/MySQL/Apache. (If you can install Drupal or Wordpress you can probably install Friendica) A single Friendica installation supports up to several thousand members. Every Friendica installation can connect with any other to create a social network without limits. (And one that nobody can own or control). Friendica can also connect to your friends in other social networks - such as Status.Net, identi.ca, GNU-social, and Google Buzz. The list of supported networks is growing.