KiCad - A Cross Platform and Open Source Electronics Design Automation Suite
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.
Fritzing - Fritzing is an open-source initiative to support designers, artists, researchers and hobbyists to...
upverter - Upverter makes it easy to design and share electronics on the web.
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.
Ktechlab - KTechLab is an IDE for microcontrollers and electronics.