Unlock Untracked:
Get any medal in all courses in RACE mode.

To Unlock Pipedream:
Get any medal in all courses in SHOWOFF mode.

Hints

Unlock Uberboards:
Unlock all of the tricks for a character to access their uberboard, which is their best board.

Metal Outfit:
Get your raking to master mode by getting 10 gold medals on different stages.

Change the Future...Kind Of:
Don't like your score on showoff for Aloha Ice Jam, just before you get to the finish line push the Y button to warp. You will then be warped back to the beginning of the cave, and have the chance to get some of the bonuses that you may have missed before.

Thanks to Revolution readers Andre Fields, pablo, Big B and Darrel McDaniel!