Enter these on the Passwords Screen for Madden Cards under the My Madden menu:

Password - Effect

KL0CRL - When this card is played, this will pump up the crowd for the 49ers.
B1OUPH - When this card is played, this will pump up the crowd for the Bears.
DRL2SW - When this card is played, this will pump up the crowd for the Bengals.
1PLUYO - When this card is played, this will pump up the crowd for the Bills.
3ROUJO - When this card is played, this will pump up the crowd for the Broncos.
T1UTOA - When this card is played, this will pump up the crowd for the Browns.
S9EWRI - When this card is played, this will pump up the crowd for the Buccaneers.
57IEPI - When this card is played, this will pump up the crowd for the Cardinals.
F7UHL8 - When this card is played, this will pump up the crowd for the Chargers.
PRI5SL - When this card is played, this will pump up the crowd for the Chiefs.
1R5AMI - When this card is played, this will pump up the crowd for the Colts.
Z2ACHL - When this card is played, this will pump up the crowd for the Cowboys.
C5AHLE - When this card is played, this will pump up the crowd for the Dolphins.
PO7DRO - When this card is played, this will pump up the crowd for the Eagles.
37USPO - When this card is played, this will pump up the crowd for the Falcons.
C4USPI - When this card is played, this will pump up the crowd for the Giants.
MIEH7E - When this card is played, this will pump up the crowd for the Jaguars.
C0LUXI - When this card is played, this will pump up the crowd for the Jets.
3LABLU - When this card is played, this will pump up the crowd for the Lions.
4HO7VO - When this card is played, this will pump up the crowd for the Packers.
F2IASP - When this card is played, this will pump up the crowd for the Panthers.