installable social networks

Top picks:

http://friendica.com/

http://www.boonex.com/dolphin

http://movim.eu

http://elgg.org/

http://www.jomsocial.com/ : Joomla based

http://www.anahitapolis.com/

A few more options here:
http://zoomq.qiniudn.com/ZQScrapBook/ZqSKM/data/20081021154233/index.html