There already have been a lot of great suggestions by the illustrious members of this community. I want this to continue and hopefully become a resource where everyone can gain an intricate knowledge of the game we love. Thanks to everyone who contributes.

My original text:

I've always loved football. I started playing when I was 7 and didn't stop until my high school glory days ran out. However, I was never blessed with the opportunity to play under great coaches (or a great team for that matter). I would like to expand my knowledge of the game starting with the defense. I figure other people may feel the same way, so I thought it would be a good idea to have a FanShot to suggest and discuss books and websites that are informative. Smart Football has been a good starting place for a little bit of everything, but I really want to learn more.

Field Gulls, what are your favorite books and websites that truly break down the X's and O's of the game we obsess over?

Suggested Sources:

Field Gulls

Smart Football

Football Outsiders

Advanced NFL Stats

Pro Football Reference

Zone Blocking System - An FSU Perspective

Pete Carroll 4-3 Under Defense

Pete Carroll 4-3 Under Defense - Blitzing

Monte Kiffin Defense Part 1

Monte Kiffin Defense Part 2

Football Defense