FreeCAD is an open source CAD/CAE, based on OpenCasCade, Qt and Python.
FreeCAD features some key concepts like Workbenches and Macro recording with ability to run as a server and dynamically loadable Application extensions and its designed to be platform independent.
FreeCAD is also one of the few open source CAD programs with actual nice 3D-support perfect for procedural geometry.
The portable version of the software can be found here.
FreeCAD is not available for Handheld
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