Logisim - Logisim is an educational tool for designing and simulating digital logic circuits.
Pspice - OrCAD PSpice technology provides the best, high-performance circuit simulation to analyze and refine your circuits, components, and parameters before committing to layout and fabrication
Digital - A simulator for digital circuits.
Oregano - oregano - An electrical engineering tool for GNOME
Logicly - - Design circuits quickly and easily with a modern and intuitive user interface with drag-and-drop...
PCBWeb - PCBWeb is a 100% free Windows desktop CAD application for designing and manufacturing electronics...