Blender - Blender is the open source, cross platform suite of tools for 3D creation.
SketchUp - 3D for Everyone
Sculptris - Sculptris: Enter a world of digital art without barriers.
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
Sketchfab - Sketchfab is an industrial design software tool is useful for ideation and for beginners in the industrial design field.
DraftSight - Discover Dassault Systèmes®' DRAFTSIGHT™ Professional CAD software that lets you create, edit, view and markup any kind of 2D drawing. Learn more here.