Snowboard Kids 
All courses, snowboards, and snowboarders
At the title screen, press Down on the control stick, Up on the control stick, Down on D-pad, Up on D-pad, C-Down, C-Up, L, R, Z, Left on D-pad, C-Right, Up on the control stick, B, Right on D-pad, C-Left, and then Start. You should then hear a "Yeah!", showing that the code worked.

Ice Board
Buy all the normal boards.

Feather Board

Get 2700 points in the trick skill game.

Star Board
Get gold cup all the tracks including three extra tracks.

Hidden Quicksand Valley Track

Collect all Gold Cups on tracks 1 to 6, and you will be rewarded with the desert track, Quicksand Valley, and an additional snowboard.

Hidden Silver Mountain Track

First you must earn gold cups on tracks 1 to 7 to open up Quicksand Valley. Now go for the gold on Quicksand Valley, and Silver Mountain will open up.

Hidden Ninja Land Track

First you must earn gold cups on tracks 1 to 8. After you opened up Silver Mountain, come in first to get a gold cup and you will be treated to an ending sequence with all the characters. Track 9, Ninja Land, will now be open.