IBM's free Many Eyes website allows anyone to easily upload, visualize, and discuss data. ManyEyes.js was my experiment porting several of the Many Eyes visualization components from Java/Swing to HTML5/Canvas/JavaScript, allowing them to run in modern browsers without any plugins.
I also created a declarative API allowing web site developers to use simple declarative HTML markup to add visualizations to their websites. A bookmarklet allowed users to inject the ManyEyes.js library into arbitrary websites, automatically detecting and visualizing tabular data in the context it was encountered.