So, i looked at Shape3D - it's very nice BTW. However, isometric projection is not rendered in true 3d space with vanishing points, real-world geometry, etc. It is an approximation, an architectural geomoetry I suppose. Also, there is no requirement for lighting, etc.
Also, I installed the plugin and looked at the tutorial - which works great for cubes, but what if my shape has arbitrary dimensions? It wasn't clear how I would tackle that with shape3d.
Maybe I'm missing something. Let me know.
Wikipedia on Isometric Projection:
http://en.wikipedia.org/wiki/Isometric_projection
This covers all the nitty-gritty, variants and differences between 3D, true isometric, etc.