LibreCAD is a free Open Source CAD application for Windows, Apple and GNU/Linux. Support and documentation is free from our large, dedicated community of users, contributors and developers.

http://librecad.org/cms/home.html
http://en.wikipedia.org/wiki/LibreCAD
http://wiki.librecad.org/index.php/Main_Page
http://sourceforge.net/projects/librecad/
https://github.com/LibreCAD/LibreCAD