KiCad - A Cross Platform and Open Source Electronics Design Automation Suite
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Proteus PCB design - Proteus PCB design combines the schematic capture and ARES PCB layout programs to provide a...
FreeCAD - An open-source parametric 3D modeler
EasyEDA - EasyEDA - Web-based EDA suite; runs in browser.
Sculptris - Sculptris: Enter a world of digital art without barriers.