I used to code some simple demos using Three.js and I highly recommend it. You may checkout its homepage and some demos at https://github.com/mrdoob/three.js
FYI, there's a wiki page for various Javascript game engines where you may find some nice projects: https://github.com/bebraw/jswiki/wiki/Game-Engines
and a wiki page for 3D engines: https://github.com/bebraw/jswiki/wiki/WebGL
