py3d is a Python-based procedural modelling and animation tool for building 3D scenes. It's fun to play with and even useful for teaching 3D geometry and transformations. Runs on SGI IRIX and Linux.
Unfortunately Py3d is built on top of the now defuct SGI OpenGL Performer scene graph library. I'm still evaluating alternative scene graphs: current candidates are Irrlicht and Panda3D.