D3.js looks like a promising free JavaScript-framework, to visualize data-driven documents and infographics. The special thing about this framework it, that D3 is not another ordinary visualizing-framework, that you have to learn and adapt. It is much more lightweight in its nature:

“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. With minimal overhead, D3 is extremely fast, supporting large datasets and dynamic behaviors for interaction and animation.”

There could be much more said here, but why not directly head over to the D3.js-page? There is everything explained in an elegant way.