LinuxCNC (the Enhanced Machine Control) - LinuxCNC: an open source CNC machine controller. It can drive milling machines, lathes, 3d printers, laser cutters, plasma cutters, robot arms, hexapods, and more.
Mach3 - Mach3 is very popular among the Hobby CNC community.
PyCAM - PyCAM is a toolpath generator for 3-axis CNC machining.
Edgecam - The industry standard CAD neutral Production CAM system
Vectric Aspire - The complete software solution for CNC Routing,
jscut - A CAM in your browser! Convert your SVG files to CNC cutting paths with this tool.