At the main menu, select the My 2K7 option, then choose the "Enter Cheat Code" selection. Then enter the codes to unlock the following:

Password - Effect

Derek Jeter - Unlock all bonuses.
Black Sox - Unlock all cheats.
Game On - Unlock all extras.
triplecrown - Unlocks a card that increases the hitting of the 3rd, 4th, and 5th batter for 50% of one game.
mightymick - Unlocks a card which increases a teams power rating by 25% for one inning.
m4murder - Unlocks a card which increases chances of hitting home runs for one game.
phmantle - Unlocks Mickie Mantle as a pinch hitter.
themick - Unlocks Mickie Mantle in free agency.