http://machinetouch.appspot.com/svgEngraver.py
http://kalyaev.com/2010/20100402/tut01/tut01.html
http://reprap.org/wiki/PCB_Milling http://replicat.org/generators
http://www.heeks.net/
http://www.probotix.com/cnc_software/
http://www.scorchworks.com/Fengrave/fengrave.html
http://www.alessandrofrancesconi.it/projects/morphop/