Circuit Simulator - Animated electronic circuit simulator using ideal components to visualize voltage and current.
Logisim - Logisim is an educational tool for designing and simulating digital logic circuits.
KiCad - A Cross Platform and Open Source Electronics Design Automation Suite
BOOLR - Open-source digital logic simulator
Logicly - - Design circuits quickly and easily with a modern and intuitive user interface with drag-and-drop...
CircuitVerse.org - CircuitVerse is an online community driven platform to design and simulate digital logic circuits.