I created a logic circuit simulator called GatePlay - aimed for casual use by beginners/students, but the simulation is not over simplified.
I know of a couple of small bugs already, but feedback would be awesome!
Use it: http://greglo.github.io/gateplay/ GitHub: https://github.com/greglo/gateplay
Show HN: GatePlay, HTML5 logic circuit simulator
greglo.github.io