Blender - Blender is the open source, cross platform suite of tools for 3D creation.
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
Sculptris - Sculptris: Enter a world of digital art without barriers.
FreeCAD - An open-source parametric 3D modeler
Sketchfab - Sketchfab is an industrial design software tool is useful for ideation and for beginners in the industrial design field.
SketchUp - 3D for Everyone