FreeCAD is a general purpose parametric 3D modeler.

FreeCAD is aimed directly at mechanical engineering and product
design but also fits in a wider range of uses around engineering,
such as architecture or other engineering specialties.

FreeCAD features tools similar to Catia, SolidWorks or Solid Edge,
and therefore also falls into the category of MCAD, PLM, CAx and
CAE. It is a feature based parametric modeler with a modular software
architecture which makes it easy to provide additional functionality
without modifying the core system.

       FreeCAD is under heavy development and might not be
                    ready for production use.

WWW: http://www.freecadweb.org/