Let's face it, most guys like football. To be fair, some women like football, too. But most women I know just follow their hometown team. Maybe they know a few key players and whether they're likely to get to the playoffs this year. Most guys actually follow football, meaning they don't just know stats for their favorite team or the other teams in the same division. They know key players for all the teams and whether they're having a good year, they know win/loss percentages, who's destined for the Super Bowl and who won't even get close to the playoffs. Not to sound sexist or anything, but women don't usually get into that kind of detail when it comes to football.
I grew up watching football with my dad and enjoyed football more than my two brothers. (By the way, I am a big Chicago Bears fan.) I started dating my now-husband during baseball season (I'm not a big fan but who doesn't love the Cubbies?) but it was during football season that he fell in love with me. I think it was the time that I yelled "Come on! My grandma can tackle better than that!" or maybe it was when I screamed "What the hell, no flag?! That was pass interference!" He'll tell you it was when he realized that I actually know what a bootleg is (it isn't a reference to the shape of Italy), I can identify a shotgun formation and point out when it would be a good time to go for it on 4th down. Most of all, I think he likes the fact that other guys are impressed by my football knowledge.
I'm not suggesting that you single ladies out there learn football to get a man. Although there are those who recommend it. I agree with this woman that it's better for single girls to look for men at sports bars than at night clubs. For my money, I'd much rather be eating spicy wings and watching football than drinking overpriced alcohol and trashing my hearing with crappy techno music. But I don't agree with her assertion that men who can commit to a favorite sports team can commit to a woman. There are plenty of men who have no problem sticking with their team but who couldn't commit to a woman to save their lives.
I'm simply saying that you can really impress men, if you're so inclined, by knowing your football. So, to help you in that endeavor, here are a few websites and books to get you started. The most comprehensive website is probably this about.com article. It really covers the basics and is good if you know nothing about football. There are others but most of them that are geared towards women are rather sexist or just too basic. You aren't going to impress anyone after reading those articles.
As far as books go, there's the usual "for Dummies" and the "Idiot's Guide" series. Frankly, I don't like to label myself as a dummy or an idiot so the titles bug me. But those books are often helpful* and these might be a good place for more than basic information.
One of my favorite football books is this one:
It won't really teach you about the game. But you'll get a good laugh and maybe be a better spectator. Making a few of the recipes might be impressive, too.
*Totally unrelated aside here - the best in the series that I've read is The Complete Idiot's Guide to Middle East Conflict, 3rd Edition (The Complete Idiot's Guide). Many of the information on this conflict is biased in one direction or the other. This book reviews the history of the Middle East (highly summarized of course) and describes the seeds of the conflict that have been growing for ages. It doesn't blame Israel and it doesn't paint Muslims as crazy terrorists. It's a very interesting read if you want a fairly balanced view of the situation.