Unlock Galaxy Circuit:
Finish each race as one of the top three.

Unlock Reverse Mirror Tracks:

Win a gold medal on the Galaxy Circuit with any character.

Unlock Darth Vader:
Win a gold medal on the Galaxy Circuit with Anakin Skywalker.

Quick start:
Hold R2 + X (accelerate and jump) a moment before the final start light illuminates to get a speed boost off the starting line.

Unlock AAT battle tank:
Press Circle, Square, Circle, Square at the main menu.

Unlock Boba Fett:
Press Square, Circle, Circle, Square at the main menu.

Unlock Naboo Kaadu racers:
Press L1, R1, L2, R2 at the main menu.

Unlock Shark racers:
Press Up, Right, Down, Left, Select at the main menu.

Unlock Infinite boost:
Press L1, R2, L1, R2, Square, Select at the main menu.

Unlock Space Freighter arena:
Press L1, R1, Select, Circle at the main menu.

Switch language:
To German: Press Select, Select, Select, L1 at the main menu.
To Spanish: Press Select, Select, Select, R1 at the main menu.
To French: Press Select, Select, Select, R2 at the main menu.
To Italian: Press Select, Select, Select, L2 at the main menu.
To English: Press Select, Select, Select, Circle at the main menu.
To Jawa: Press Select, Select, Select, Square at the main menu.
To Battle Droid: Press Select, Select, Select, Up at the main menu.

Unlock All Tracks:
Start a 2 player team game and no matter what you can't get below third place, which will give you the next track available. Repeat through all of them and you get them all.