FreeCAD is what you need for 3D cad/cam or 3d printing. And for 2D cad, or 2D cad/cam, there's the free GPL version of QCad (recommended to buy the full version for $40 to get cad/cam and more import/export file support from autocad). Anything else (librecad, openscad, Design etc) are not as well rounded imho. And then there's onshape, but that's not Free software.