Press [Ctrl][Alt][F1] in the main menu and the cheat menu appears.
 Type in;

 moremoney       - More money (I guess, you have guessed that)
 suddesh         - Invincibility
 finish          - Win current level
 go_faster       - Doubles speed
 open_the_doors  - Open all doors
 sizzle          - Light everywhere
 valentino_rossi - Drive a motor bike
 slicks          - Speed up motor bike
 shit            - Player gets older very fast

 To get to the bonus level:

 Press [Ctrl][Alt][F1][F2] together at the main menu and type in

 holidays        - Holiday bonus level
 raceway         - All tracks available

 From v1.68:

 Press in the game (not in the bonus level) [Ctrl][Alt][F10], then hold [Tab]
 down an wait for the cheat window. Here you can enter:

 shot            - Fast shooting
 racer           - More weapons
 dudodida        - No more rain (Level 5)
 pic             - Play as pig