three.js, by mr. doob, is a fantastic 3d engine for javascript that includes scenegraph (both software and WebGL/hardware accelerated versions), shading, particles, skinned animation (i think), and lighting effects. Check it out, he is a super-talented fellow.
I should add that you are going to need the newest Google Chrome or equivalent to view most of the demos, one of my favorites is: http://mrdoob.github.com/three.js/examples/webgl_materials_cars.html
