interactive information visualization
prefuse is an open-source, java-based interface toolkit for building interfactive visualizations of data. Using this toolkit, developers can create responsive, animated graphical interfaces for visualizing, exploring, and manipulating these various forms of data. Here's a cool demo showing a force-directed layout of a social network. According to the paper prefuse: a toolkit for interactive information visualization prefuse is designed to work with very large datasets. One example in the paper demonstrates using prefuse for browsing through a 600,000 node web directory.
This package looks like it will be very useful for visualizing artist and music similarity networks. Some folks over at Berkeley are doing just this with project Orpheus. Orpheus is an exploration and visualization tool for discovering the universe of new and independent recording artists. Check out the demo of orpheus. (Thanks to Brooke Maury for the prefuse tip).