Blender - Blender is the open source, cross platform suite of tools for 3D creation.
KiCad - A Cross Platform and Open Source Electronics Design Automation Suite
SelfCAD - SelfCAD is an online 3D modeling and slicing software.
Proteus PCB design - Proteus PCB design combines the schematic capture and ARES PCB layout programs to provide a...
SketchUp - 3D for Everyone
QUCS - Qucs, briefly for Quite Universal Circuit Simulator, is an integrated circuit simulator which means you are able to setup a circuit with a graphical user interface (GUI) and simulate the large-signal, small-signal and noise behaviour of the circuit.