CAD, BIM & 3D

When you visit http://www.cadlogic.com/products/draftit/index.htm you can download a free 2D CAD system for Windows. It seems to be fairly helpful while drawing, although, since it's a free basic version, expect to find limitations.

While Autodesk is promoting DWF Composer/Design Review since quite some time, they changed tactics and recently decided to make the application freely available. You can create and markup DWF documents, including printing, measuring and browsing. This was previously sold for about $200, but the price in most practical circumstances was about $100 or even free. Windows only. To view DWF files on a Macintosh, you can use Project Freewheel or McDwiff (which connects to Project Freewheel in the back).