These codes should be entered at the title screen while the words "Press Start" are flashing:
Level Select- Press L1, R1, L2, R2, Square, X, Circle, Square, Square, Circle, X, Triangle. Push Start for the Main Menu and there will be a Level Select option. Highlight it and press X to skip to any level.
All Weopons and Ships- Press L1, R1, L2, R2, Up, Down, Right, Left, Left, Right, Down, Up. All ships and weopons should now be available.