nanoCAD is a professional and simple CAD software, with full *.dwg support. Developed by Nanosoft
License: Freemium
Apps available for Windows
LibreCAD is a free Computer-aided design (CAD) application for 2D design. It works on Linux, OS X, Unix and Windows operating systems. Developed by Ries van Twisk
License: Open Source
Apps available for Mac OS X Windows Linux PortableApps.com