KiCad - A Cross Platform and Open Source Electronics Design Automation Suite
Fritzing - Fritzing is an open-source initiative to support designers, artists, researchers and hobbyists to...
OrCAD - OrCAD is a great tool for creating electronic designs that sell.
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.
PADS PCB Design - Best-in-class PCB design tools at unbeatable prices
Autodesk EAGLE - Autodesk EAGLE is an electronic design automation (EDA) software.