D3.js is a powerful javascript library written initially by Mike Bostock who was working for the NY Times to create interactive visualisations of data. D3 stands for Data Driven Documents and uses HTML, SVG and CSS to render data as customisable visualisations.
Processing is a language for coding intereactive visualisations. The software itself is open source and can do accelerated 2D and 3D with OpenGL integration cross platform. There are many libraries extending the core software. There is also a browser based processing js library.