OpenSCAD - OpenSCAD is a software for creating solid 3D CAD objects.
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
FreeCAD - An open-source parametric 3D modeler
SketchUp - 3D for Everyone
ImplicitCAD - ImplicitCAD is a programmatic CAD program, implemented in Haskell.
CadQuery - CadQuery is a parametric cad script framework