KiCad - A Cross Platform and Open Source Electronics Design Automation Suite
FreeCAD - An open-source parametric 3D modeler
LTspice - LTspice® is a high performance SPICE simulation software, schematic capture and waveform viewer with enhancements and models for easing the simulation of analog circuits.
SolidWorks - Dassault Systèmes SolidWorks Corp. develops and markets 3D CAD design software, analysis software, and product data management software. SolidWorks is the leading supplier of 3D CAD product design engineering software.
Fritzing - Fritzing is an open-source initiative to support designers, artists, researchers and hobbyists to...
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.