Blender - Blender is the open source, cross platform suite of tools for 3D creation.
FreeCAD - An open-source parametric 3D modeler
MakeHuman - MakeHuman is a free, open source, interactive modeling tool for creating custom 3D human characters.
meshmixer - meshmixer is an experimental 3D modeling tool for making 3D mashups without too much hassle.
Bforartists - Bforartists is a fork of Blender.
Onshape - Onshape is the first full-cloud 3D CAD system. It runs in a web browser and on any mobile device.