I've just been doing some concept design work in 3DS Max. With the design finished I needed to extract a 2D drawing that I can clean up in Autocad and then pass on to the set builders. It's a little bit of workflow that is always helpful to do with architectural projects, say when you're working on a competition, but can be a bit of a pain.
Well, I'm quite pleased with this workflow in the end. I viewed my 3D model in elevation or plan and drew splines over it using the 2.5 snap. This is pretty quick to do but can leave you with lines floating all over the place in 3D space which are then a pain to work with in Autocad. Scribe by SiNi Software has a flatten spline button, and with a click of a button your splines are all flattened to the C-Plane. Ta da!