Hmmm...not quite, but I have a more specific request now that I should have outlined in my first post. I'm actually looking for a "Logic Gate Simulator" that will run simulations with logic gates that I set up (AND, OR, NOT, XOR, etc.).
I found this, but need to know from someone who has used a logic gate simulator on a Macintosh:
http://www.logicworks4.com/