I like the Texans, only problem with them is the division they play in. The Colts and Titans are, well, the Colts and Titans. And the Jaguars aren't spectacular but they're a tough team to beat.
Oakland definately has a chance. A very young team, with a defense seriously on the rise, and an offense potentially made up of young budding stars* (if they bud) like Russell, McFadden, that receiver they drafted early who's supposed to be a speedster, Higgins, etc... in a weak division (Denver is taking a big step down in my books for the next two years), and with Kansas City rebuilding, it's Oakland and San Diego over there.
The Bengals could come out of nowhere, and they're another team that sticks out to me. With Palmer coming back, and Chad Johnson working hard, and maybe just MAYBE an emerging Cedric Benson, this team has a chance. Add in a few risks that could pan out on the defense, like Rey Mal...and Roy Williams, this team could surprise and compete with the Ravens and *gasp* Steelers.
Those are my 3 teams in that order for the AFC...as for the NFC, it's hard for me to give Detroit a chance. I think the Saints are going to win their division but I'm not so sure that would be out of nowhere. Nobody in the NFC really strikes me as a sleeper, I think it's pretty easy to separate the contenders from the pretenders.