There actually is one hack I was looking for a while back. I remember reading on a website, a guy who had ported Pitfall II to the Game Boy Color, but said that it was cancelled before release. He had made an alternate layout for the entire game, as a bonus, and released it for the original Atari 2600 game. For whatever reason, I didn't download it, and now I can't find it anywhere.
I'm sure I could ask at AtariAge, I just never think about it.