Can anybody suggest an open source "social network" application?

Here are two examples of such applications:
http://www.cooperativeresearch.org (not sure of licensing)

http://www.politicalfriendster.com (probably open source)

They have their strengths and weaknesses. I'd like to know what else is
available.
--
http://www.dailymotion.com/video/x1e...of-911-updated
http://911research.wtc7.net
http://vehme.blogspot.com
Virtus Tutissima Cassis