I use EMC2 - its great! The EMC2 community is a useful source of information about linux CAD and CAM

you could start here on their wiki:
http://wiki.linuxcnc.org/cgi-bin/emc...ode_Generators

I use Vectric Cut2D and Cut3D myself, but if you know python then there is pycam which can do more than just 2D