Digital
Logisim
BOOLR
CircuitVerse.org
Wired Logic
Logisim Evolution
Hradla
SocialScore.io
PSIM
Logisim
Circuit Tree
CircuitLab
Circuit Simulator
QUCS
LTspice
Pspice
Digital
PSIMLogisim - Logisim is an educational tool for designing and simulating digital logic circuits.
BOOLR - Open-source digital logic simulator
Circuit Tree - Design and order Boards in Minutes
CircuitVerse.org - CircuitVerse is an online community driven platform to design and simulate digital logic circuits.
CircuitLab - Sketch, simulate, and share your circuits, entirely in your browser -- no install required.
Wired Logic - Wired Logic is a pixel based logic simulator.