Logisim
Digital
LTspice
BOOLR
Logicly
Fritzing
Circuit Simulator
CircuitVerse.org
Riviera-PRO
Synopsys VCS
ModelSim
Cadence Incisive
VCS
ESO Scheduling
gEDA Project
Circuit Tree
Logisim Riviera-PRODigital - A simulator for digital circuits.
Synopsys VCS - HDL Simulator of System Verilog, Verilog, and VHDL for ASIC design and verification.
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.
ModelSim - ModelSim-Altera Software
BOOLR - Open-source digital logic simulator
Cadence Incisive - System Verilog, Verilog, VHDL, SystemC HDL Simulator for ASIC Design and Verification