I found this amazing 3d interactive visualization of social networks while browsing posts from my friends' friends' blogs on Facebook:
Skyrails is developed by Yose Widjaja (Google / SML Wiki). When he's not busy working on Skyrails, he writes Flash games. Very cool.
+ Skyrails Blog: official blog by the author
+ Download Skyrails beta: PC only, one generation before the current release, published on 2007-10-10
Related SML Universe
+ SML Wiki: Social
+ SML Wiki: Network
+ SML Wiki: Visualization