All tracks:
At the Title screen, press Up, Left, Down, Right, B, A, B, Right, Down. You'll hear a sound to confirm entry. This will unlock all of the tracks.

All cars:
At the Title screen, press Up, Down, Up, B, A, Left, B, B, Down. You'll hear a sound to confirm entry. Now all of the cars are playable.

All Seasons:
At the title screen, press Up, Left, Down, Right, B, A, B, Right, Down.

2 More Cars:
Two additional bonus cars are unlocked by playing in arcade mode. The Renault Maxi Megane is unlocked after finishing in seventh place or better on the "Easy" difficulty setting. For the Toyota Corolla Tien, highlight the Toyota Corolla on the car selection screen, hold L, then select that car.

Higher framerate:
At the Main Menu, press Up, A, Down, Down, Left, Right, B, B, Down. You'll hear a sound to confirm entry.

Alternate car colors:
At the Car Selection screen, highlight a car and press L to change its color.

Control replays:
During a replay, press A, Y, or X to change the view and press B to return to the normal replay angle.

Secret Rally Track:
Finish in first place in every year under "10 Year Championship" mode.

Thanks to Revolution readers Apu Flippy, Kevin, Richard Roodbeen and George B.!