OpenSCAD - OpenSCAD is a software for creating solid 3D CAD objects.
FreeCAD - An open-source parametric 3D modeler
ImplicitCAD - ImplicitCAD is a programmatic CAD program, implemented in Haskell.
CadQuery - CadQuery is a parametric cad script framework
PLaSM - Programming Language of Solid Modeling
BRL-CAD - BRL-CAD: Open Source Solid Modeling