If, like me, you are a fan of both NFL football and picayune legalistic minutiae, I strongly recommend reading through the archive of the Jerry Markbreit "Ask the Referee" column from the Chicago Tribune. (Thanks, Mike.) You can learn rules about a pass batted back to and caught by the quarterback (no second pass allowed), returning a short field goal attempt (you must catch the ball on the fly, you get the original spot if you take a knee in the end zone, etc.), and pass interference and a personal foul on the same play (both penalties enforced if and only if the same conduct led to both penalties--such as interferencing by committing a major facemask). And that's just this week!