I've been doing 3D modeling for lighting simulation and I found two reasonably well-supported solutions: VTK and OpenSceneGraph. VTK generally has a research slant and has what I believe are reasonably strong Python bindings. OSG is closer to VR/AR/Flight Simulation applications and the Python bindings are pre-alpha--you'll probably have to roll your own for some purposes. Both are OpenGL based; if you need an easy Windows install you'll have to go with something that supports DirectX.
If your app is simple, you might just be able to write OpenGL code. Anyone who knows of other reasonably current libraries, please follow up--there are a lot of libraries that don't seem to see much activity, and I'm not sure if this is because they are complete or because they are not much used. -- http://mail.python.org/mailman/listinfo/python-list