While at the game's Title Screen:

Master Code
R1, R1, Up, Down, R2, R2, Left, Right

$10,000 In Car
Up, Down,Left,Right,Up,Down,Left,Right,R1,Left,Left

Pit crashing
Go into the pits at the end of pit lane. You can crash into cars, which shows on the tack.

Bonus options
The following bonuses can be unlocked during game play by doing well and earning points:

AI Vengeance: AI cars retaliate when hit.
Front Wheel Drive: Car has front wheel drive.
Hardcore Physics: Hardcore realism.
Horn Ball: Press Up to shoot a paintball.
Horn Mortar: Press Up to shoot an explosive mortar.
Insane Racecar: Press Up to jump.
Mini Cars: Smaller cars.
Monster Cars: High suspension.
Oh Dear: One car on track replaced by monstrous-sized crew member.
Super Draft: Faster draft speed.

Race as Richard Petty
To race as Richard Petty you must get a bronze or better in all the Beat the Heat challenges