Cross-platform Open-source 2D CAD
DXF2GCODE: converting 2D dxf drawings to CNC machine compatible G-Code
3D/2D Concrete Reinforcement in Bentley MicroStation
2D CAD software
SOLVESPACE is a free (GPLv3) parametric 3d CAD tool.
Did you ever made a production machine on steroids?
2.5D CAD CAM emphasis on CAM and toolpaths
Open Source CAD