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
Altium PCB Designer - Altium offers a top-notch, best-in-class PCB Designer to give engineers the tools they need to interlink with each side involved in the electronic design process.
SketchUp - 3D for Everyone
Ktechlab - KTechLab is an IDE for microcontrollers and electronics.
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.