http://raphaeljs.com/touches.html
Based on tutorial at http://net.tutsplus.com/tutorials/javascript-ajax/an-introduction-to-the-raphael-js-library/
Uses Minkovski sum technique to properly bounce a 2D ball off a circular wall. For more information, see: http://gamedev.stackexchange.com/q/29650
A simple demo of raphael.js just to get started.
A demo in several parts.