Hold Square at the 'Options' screen and then press Up, Circle, Down, Circle, Left, Right, Left, Right, Circle. You'll know if you've entered the code correctly because a new window called 'Secret' will appear at the bottom of the 'Options' screen. Now go to Single-Player mode and enter 'NORTHEND' (case sensitive and without the quotes) as a name and ALL courses and cars (ice-cream van and cow-catcher (UFO) included) will be unlocked.

When you complete Time Attack mode you will get another engine which is an improvement from the one you were using.

More Boards :
An additional snowboard is unlocked each time your snowboard earns a new rank.

Alternate Costumes :
Successfully complete all green or blue square tricks to unlock two additional sets of costumes.

Running Man Mode :
Hold L1 + L2 + R1 + R2 and press Square, Triangle, Circle, Cross, Square, Triangle, Circle, Cross at the options screen. repeat this code to disable it's effects.

All Course Hints :
Hold L1 + L2 + R1 + R2 and press Circle, Cross, Circle, Cross, Circle, Cross, Circle, Cross. repeat this code to disable it's effects.