Blender - Blender is the open source, cross platform suite of tools for 3D creation.
3D Cityplanner - Urban and real estate development at your fingertips. With the 3D Cityplanner it’s possible to create, visualize, analyze and share 3d plans online.
SketchUp - 3D for Everyone
AC3D - AC3D is a 3D software for games, virtual reality and flight simulation, scientific, medical and general data visualisation, rapid prototypes of 3D designs, 3D printing, Google Earth, X-Plane, Second Life and more.
Modelur - Save time and make well-informed decisions during early stages of urban design.
FreeCAD - An open-source parametric 3D modeler