Granted, it's the off season, but football really never takes a break.  Check out the earliest known footage of football in this clip from 1903.

 

The real game footage gets started a little after the 2 minute mark and it's crazy to see the way that the game used to be played.  By no means am I a "Back In The Good Old Day" type of person, but you see this game and can just tell there was something about the game before all the money was involved.