This is a guest post from Micheal Kavanagh, a huge football fan who really knows his stuff. I strongly recommend you follow him on Twitter.
#6 Oklahoma v Texas: The Red River Rivalry/Shootout
Started in 1900 and has ran continuously since 1930. One of the major rivalries because it usually has title considerations on the line. In 2005 the name was changed from 'shootout' to 'rivalry' so as not to give the impression of condoning gun violence.
#5 Alabama v Auburn: The Iron Bowl
Played since 1893 with only one tie, disagreement between the schools began immediately as Alabama considered the game to be the final matchup of the 1892 season and Auburn recorded it as the first of 1893. The game was cancelled in 1907 as the teams could not agree on where the refs would come from. It was renewed in 1948. In 2011, the rivalry took a nasty turn with the poisoning of the 130-year-old oak trees at Toomers Corner on the Auburn campus.
#4 Army v Navy
Started in 1890 and has ran continuously since 1930. Long gone are the days when either team were involved in title races but the game is still nationally televised. For seniors it's most likely the last game they'll play.
#3 Harvard v Yale: The Game
Started in 1875 and the first game in the rivalry was the second football game played between US colleges featuring a ball-carrying form of the game, with those rules being adopted by other schools. Myth has it that before the 1908 game, Harvard coach Percy Haughton strangled a bulldog to death in the locker room to motivate his players.
#2 Florida v Georgia: World's Largest Outdoor Cocktail Party
Officially known as the Georgia v Florida Football Classic but better known as the World's Largest Outdoor Cocktail Party. These two teams can't even agree when the rivalry started, Florida says 1915 and Georgia says 1904. They have met every year except one (1943) since 1926.
#1 Lafayette v Lehigh: The Rivalry
Started in 1884 and has ran continuously since 1897, the only interruption in the series was in 1896. It is the longest running series in college football and pre-dates trophies with the winner simply getting a game ball.