Freebase is one of my two new favorite toys, the other being my Xbox 360. Freebase is a free database of the world's knowledge, licensed under Creative Commons and provides an API to enable mashups and applications. That means a powerful driving force for data visualization.
Attend the User Group Meeting
On June 17, Freebase is holding their bimonthly user group meeting in San Francisco. They'll be presenting Freebase's new features as well as discuss some interesting mashups and visualizations. So if you're in San Francisco, RSVP now, and go get some free pizza, beer, and a t-shirt.