All I know is that I believe this list originally appeared on nfl.com. I want to give appropriate credit and, better yet, link to it, but I haven't found the source as of yet. I remember it floating around on e-mail, however, and I wanted to give it a more permanent home. This copy I found on a message board.
AFC (Animal Football Conference)
Rams (close enough)
Random Animals Division
NFC (Non-Animal Football Conference)
Old West Division
Texans (would've been better if they were the Oilers, but this will do)
Fighting and Plundering Division (my favorite --Cyg)
Some of those divisions would be fairly competitive, but the AFC Bird and AFC Random Animals divisions would need a little work.