Nearly newbies view so far .... 2/2.5D toolpath generation, CamBam is pretty good, full flavour version runs for 40 starts before needing purchase , but will sit miinmised happily.

Inkscape is free vector based drawing with good inbuilt bitmap tracing from Portrace

Inkscape. Draw Freely.

DXF export improved with

Big Blue Saw - Big Blue Saw's DXF Export For Inkscape

Engraving and V Carving F-Engrave:

http://home.comcast.net/~sskroch/Fengrave/fengrave.html

For more engineering drawing, ViaCad 2D/3D,not free , good DXF export in 2d and Sketchuo style push/pull tool for 3D

ViaCAD 2D/3D | Consumer CAD Software | PunchCAD

Site worth looking around

cnc4free.org homepage