Baseball Prospectus is awesome (their 2004 book is due in a few weeks) and Basketball Prospectus is really good (though the website was stale for a month), but Football Prospectus is a disappointment. An article like this is an example. The author makes some huffy judgments in hindsight (a lot of sports criticism is made in hindsight which is only valuable if some lesson can be extracted and used for predicting the future, but that's a bar that's rarely met), admits he was absolutely wrong about a lot of teams (the honesty is admirable, but it's about as soothing as hearing your financial advisor admit he goofed by investing your 401K in Enron stock), and strays into some random commentary on American Idol at the end to inject some humor, I suppose (if you don't have much insight to add on football, why do we want to hear you critique reality TV?).
Maybe, as Josh Levin wrote in Slate, it's just too difficult with the tools available today to model the sport of football with much accuracy.