The Texans are a good team on the brink, although I think that defense backtracked this year. Still Steve Slaton is the most underated back in the NFL, and Matt Schaub is a tremendous QB when healthy.
Packers defense needs some work/get younger. Aaron Rodgers is definately somebody you can build your offense around, and it's looking like Packers made the right decision in letting Favre walk.
I'm not sure about Washington. I don't know if Haynesworth and Hall are enough to close the gap between them and the rest of a very tough NFC East, especially when it's their offense that needs work.
Bills are in a simliar situation as the Texans, although I don't think they are as good as Houston even with the addition of Terrell Owens.
I don't agree with the Chiefs, but I understand why they would be mentioned. They play in a very soft division, and if they can pull off an upset or two they just might sneak their way into the playoffs. They also made a tremendous upgrade at the head coaching position, when they fired in my opinion the worst head coach in the NFL, Herm Edwards.
Some other teams I would mention.
The Cleveland Browns. Had alot of injury problems last year, but Brady Quinn is now the QB, and he didn't look all that bad in the limited playing time he had. Also I think they updgraded their head coach with the hiring of Eric Mangini who was simply the fall guy in New York for bad front office decisions, and did not deserve to be fired in my opinion. Finally if Braylon Edwards can recover from that horrendous season he had last year, the Browns could be a contender once again.
The San Francisco 49ers. Mike Singletary is quietly building a winning team in San Francisco. His first step was to get rid of all the bad apples in San Fran which were preventing that team from going anywhere. The next step is to bring in talent. If San Francisco can pull of one or two good drafts they could find themselves as the best in the west for some time.
The Cincinnati Bengals. The defense did improve from the year before, although they still can't sack anyone. Carson Palmer will be back with a clean bill of health this year, and having a guy like that at QB will always put you in a position to win games.