electrical circuit simulator: experiment or learn circuitry fundamentals
MacBreadboard is a Digital Electronics Breadboarding Simulator.It has a very unique interface in which you "move" chips & wires on a virtual breadboard. MacBreadboard and WinBreadboard (the PC version) are used in many colleges and universities around the world. It's ideal for prototyping designs on the computer before going into the lab, or in situations where using actual breadboards is not practical for some reason.The Full product includes 78 simulated TTL chips and it can even display timing diagrams.
I don't believe this works (that is, executes at all) on a modern Mac. I tried it on a Macbook Pro, and it just kept unpacking and packing between two formats. Please try it and if you agree, remove from the site!