Blender - Blender is the open source, cross platform suite of tools for 3D creation.
FreeCAD - An open-source parametric 3D modeler
Sculptris - Sculptris: Enter a world of digital art without barriers.
ZBrush - ZBrush is a digital sculpting and painting software solution.
meshmixer - meshmixer is an experimental 3D modeling tool for making 3D mashups without too much hassle.
Sketchfab - Sketchfab is an industrial design software tool is useful for ideation and for beginners in the industrial design field.