The Origami3D Engine is a 3D engine written entirely in JavaScript, using only the 2D context of the Canvas element to render 3D images. It uses the pinhole camera model, affine transforms and the HTML5 Canvas drawing API to render the 3D images.
The engine and examples should work in all modern browsers (Chrome 7+, Firefox 3.5+, Internet Explorer 9+, etc), although it might run quite slow in some browsers on certain platforms.
All of these examples and the engine are available in this public subversion repository.