Fritzing - Fritzing is an open-source initiative to support designers, artists, researchers and hobbyists to...
KiCad - A Cross Platform and Open Source Electronics Design Automation Suite
CometCAD - Circuit schematic and layout editor program for Windows 2k, XP, Vista and 7
Circuit Simulator - Animated electronic circuit simulator using ideal components to visualize voltage and current.
LibrePCB - LibrePCB is a free EDA software to develop printed circuit boards.
Virtual Breadboard - It is a circuit simulator on a virtual breadboard.