Is there such a thing as free signals to my satellite dish? If yes, what kinds of signals do they carry (ClearQAM, ATSC, etc) and how can I determine which ones are available in my area?

I live in Phoenix Arizona. I will be adding a TV tuner to my PC, and I'm interested in receiving anything I can get free and legal (from my antenna, from my COX cable, from the dish on my roof).