D3 is a small, free JavaScript library for manipulating HTML documents based on data. D3 can help you quickly visualize your data as HTML or SVG, handle interactivity, and incorporate smooth transitions and staged animations into your pages.

D3 is not a traditional visualization framework. Rather than provide a monolithic system with all the features anyone may ever need, D3 solves only the crux of the problem: efficient manipulation of documents based on data. This gives D3 extraordinary flexibility, exposing the full capabilities of underlying technologies such as CSS3, HTML5 and SVG. It avoids learning a new intermediate proprietary representation.

Requirements: Javascript Enabled
Demo: http://mbostock.github.com/d3/
License: License Free