Play as Sergei:
Enter the following as a password:
Square, L1, Square, L2, Triangle, R2, X

Play as Jackal:
Enter the following as a password:
L2, L2, circle, R2, square, R1, L1, triangle

Access the Storm Sled (single race mode only):
Goto the Options Screen and select the "load/save option". Display the password screen and enter the following:
circle, triangle, square, R2, R2, L1, x, triangle