CheatOgre.com: Burnout

Ending bonuses:
Successfully complete the game to unlock the Free Run mode (no vehicles on the road), Free Run Twin mode (two player Free Run), and Credits options.

Face Off option:
Successfully complete championship mode once to unlock Face Off 1 against the Roadster.

Roadster:
Defeat the Roadster in Face Off 1 to unlock it and Face Off 2 against another car.

Towtruck:
Play in championship mode until you unlock Face Off 2 in the special options screen. Defeat the Towtruck once to unlock it.

Saloon GT:
Defeat the Saloon GT in Face Off 3.

Bus:
Defeat the bus in Face Off 4.

Hint: Increase boost:
Drive on the wrong side of the road to keep increasing your boost. This can also be done by driving in the center of a double lane.

Drive in the wrong side of the road and use the turbo when you get it. After it is gone, your turbo will either be full or half full.

Hint: Full bonus:
Drive a perfect lap (a lap without any accidents) and your bonus will be automatically filled.

Hint: Quick start:
Accelerate immediately before the "1" fades during the pre-race countdown to start with a slight boost in speed.

Hint: Better turns:
When turning sharp corners, lightly tap the gas to turn sharper and slide less.

Hint: Rush Hour: Boost:
On Rush Hour, you can drive on the wrong side of the road to keep your boost up. If you are good enough, you can use a non-stop turbo throughout the entire course.