Skyscraper is a fully featured first-person 3D virtual building simulator, written in C++ and using the OGRE graphics engine (previous versions used Crystal Space). It’s flagship feature is an elaborate and realistic elevator simulator.
K-3D is the free (as in freedom) 3d modeling, animation, and rendering system.
MeshLab, a mesh processing system, for user assisted editing, cleaning, filterin
g and rendering of large unstructured 3D triangular meshes (typical 3D scanning meshes). The system relies for mesh processing tasks on the gpl VCG library (vcg.sf.net).
FreeCAD is a general purpose feature-based, parametric 3D modeler for CAD, MCAD, CAx, CAE and PLM, aimed directly at mechanical engineering and product design but also fits a wider range of uses in engineering, such as architecture or other engineering specialties. It is 100% Open Source and extremely modular, allowing for very advanced extension and customization. FreeCAD is based on OpenCasCade, a powerful geometry kernel, features an Open Inventor-compliant 3D scene representation model provided by the Coin 3D library, and a broad Python API. The interface is built with Qt. FreeCAD runs exactly the same way on Windows, Mac OSX and Linux platforms.