TouchGraph

"TouchGraph provides a hands-on way to visualize networks of interrelated information. Networks are rendered as interactive graphs, which lend themselves to a variety of transformations. By engaging their visual image, a user is able to navigate through large networks, and to explore different ways of arranging the network's components on screen. "

It is free software, released under an Apache Software License. It is coded in Java.

It has been used to visualize many social networks:
 * TouchGraph LiveJournal Browser
 * The whole Blogosphere
 * Your FOAF network (in this case Paolo Massa's)

TouchGraph Google Browser V1.01 http://www.touchgraph.com/TGGoogleBrowser.html

Citeseer Browser http://www.pmbrowser.info/citeseer.html

Audioscrobbler Browser (shows relations among tracks) http://www.pmbrowser.info/audioscrobbler.html

Alexa Browser http://www.pmbrowser.info/alexa.html

Amazon Browser http://www.pmbrowser.info/amazon.html

Wiki Browser http://www.touchgraph.com/TGWB_101_SS.html

TouchGraph Pubmed Browser V1.01 http://www.touchgraph.com/TGPubMedBrowser.html

and even more http://www.touchgraph.com/news.html