http://www.butterscotch.com/show/The-Top-Online-Music-Visualizations
From the page: “Stacy Reed takes us on a visual journey through some interactive sites that provide various forms of musical data . See how lyrics and artists relate to each other, get to know more about the musical interests of your friends, find out how you can install music visualizations and graphs on your own website, and even how to develop your own for free.”