We will use the simulation and visualization tool JFLAP when we work with DFA's, and perhaps a bit later on as well.
It runs best as a Java application; the easiest thing for most people will be to download a copy and run it on your own machine (Linux, Mac, or PC).
I will make it available on the department Unix machines for you to use there as well. I will not help people with problems installing or running JFLAP on Windows; I don't especially expect problems, but, while I hack, cook, clean, and take care of small children, I don't do Windows!