Unlock Everything!: This is the only code you'll need for this game as it'll unlock everything, all you have to do to enable it is press 'Start' followed by 'Tab' and input L, R, Up, Down, Left Right. If the code has been entered correctly you will hear a voice say 'COOOOOL!!' as confirmation.
Unlock Bonus Boards and Skis: To get new boards or skis in the game without using the above cheat you either win a tournament or collect a certain amount of Snowflakes.