Unlock Raven
From the main menu go to the "Options" menu, select "Cheats" then enter: RidinwRaven (you should hear a sound confirming the entry)
You can now play as Raven, just select her from the list of boarders before you begin.
Other Cheats:
From the main menu go to the "Options" menu, select "Cheats" then enter: (codes are case-sensitive)
ZiPster - Makes you go fast, even uphill.
ChillinwSteezy - Ride as a Penguin.
GimmeGimme - All levels.
StickiT - lands all jumps perfectly.
(You should hear a sound confirming the entry).
Super High Jump:

From the main menu go to the "Options" menu, select "Cheats" then enter: MegaLeg (You should hear a sound confirming the entry). Now you should be able to jump super high.
Super spins:
Select "Options" at the main menu, then "Cheats". Enter WhirlyGig as a case-sensitive code. A sound will confirm correct code entry. Press B to exit out of the cheat menu.
Low gravity:
Select "Options" at the main menu, then "Cheats". Enter MegaLeg as a case-sensitive code. A sound will confirm correct code entry. Press B to exit out of the cheat menu.
Play as Raven:
Select "Options" at the main menu, then "Cheats". Enter RidinwRaven as a case-sensitive code to unlock Raven, the girl from the original Xbox tech demos and a Xbox snowboard. A sound will confirm correct code entry. Press B to exit out of the cheat menu.
Disable tree collisions:
Select "Options" at the main menu, then "Cheats". Enter buzzsaW as a case-sensitive code. A sound will confirm correct code entry. Press B to exit out of the cheat menu.

View programmer replays:
Enter the "Replay Theater" and highlight "Hard Disk". Press Right until "Game Disc" appears to find replays generated by the programmers. To play one of those levels, select a replay then highlight "Watch Replay". Press Right until you see "Challenge" appears, then select it.