Digital - A simulator for digital circuits.
Circuit Simulator - Animated electronic circuit simulator using ideal components to visualize voltage and current.
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.
KiCad - A Cross Platform and Open Source Electronics Design Automation Suite
BOOLR - Open-source digital logic simulator
CircuitVerse.org - CircuitVerse is an online community driven platform to design and simulate digital logic circuits.