Anyone know of any software that helps plan electrical wirings? i.e. putting in lights, outlets, and switches (and how they should behave) and tells us what types of wiring to get, how to wire them, lets us simulate the circuitry - maybe even what length of wiring to get and recommended circuit breakers?

You can use Visio to do it. There are also many CAD programs that will do it.

OK - sorry - maybe it wasn't clear. :-) Not looking for just a drawing application - looking for one that assists in planning and simulating the wiring out. i.e. I enter switches, lights, fans, and outlets - and tell the software how I want them to behave (what each switch does) - and it then tells me how I need to wire them up - and maybe even simulates it on the screen (allows me to toggle switches on/off to see what that does to the lights/fans/outlets).

I never heard of anything that will do all that, I kind of doubt it exists. You may want to speak to an Electrican or and Electrical Engineer.