Free, open source D3, InfoViz, Processing.js, and Recline.js bring dynamic, interactive -- and jaw-dropping -- data-driven graphics to the Web browser
The Processing.js website provides links to copious documentation. Plus, links will guide you to more documentation for Processing itself. Best of all, there are plenty of demo applications (I counted more than 90). All include a live executable window of the visualization, as well as the source, and many provide explanations of the specific feature illustrated by the example.
This interactive display of winners of AFL/VFL (Australian Football) from 1897 to 2010 was created with Processing.js by Fink Labs. Each year is a concentric circle. Move the mouse to display the year and the team.