The PC video game Spore has a huge database of player created content and social activity publicly available via a web API.
Check it out:
http://www.sporeapi.com
They have libraries available in many languages:
http://www.spore.com/comm/developer/processing
http://www.spore.com/comm/developer/mathematica
http://www.spore.com/comm/developer/flash
among others! Looking forward to what new ways the visualization community has for looking at all of this data!
