Various cheats
Enter the following codes at the 'Hit Start' screen. 

Effect:                                Code:
Adrenaline meter always full           Down, X, X, X, R1, R1, R1
All riders have fiery hands and feet   Down, Triangle, Triangle,
                                       X, X, R1, R1
Invisible bikes                        Down, Up, Left, Down, Right,
                                       Down, Left, Up    
Level Select (Free Ride)               Square, Right, Right, Triangle,
                                       Down, Square
No on-screen displays                  Down, Triangle, Circle, X,
                                       Square
Perfect balance                        Down, Up, Circle, Down, Up,
                                       Circle, Down, Up, Circle
Unlock ''gear'' rags (rider options)   Circle, Triangle, Left, Right,
                                       Left, Circle
Unlock ''vegas'' rags (rider options)  Circle, L1, L1, Up, Up
Unlock all levels except in Road Trip  Square, Right, Right, Triangle,
                                       Down, Square
Unlock Tiki Battle mode                L1, L1, Down, R1, X, L1
Unlock Vanessa                         Triangle, Down, Left, Left,
                                       Down, Square
Unlock Bigfoot                         Triangle, Right, Up, Right, Up,
                                       Square
Unlock Mime                            Triangle, Left, Right, Left,
                                       Right, Left
Unlock Volcano                         Triangle, Up, Up, X, Up, Up, X
Unlock Day Smith                       Triangle, Up, Down, Up, Down,
                                       Square

     (Day  will  be hanging out in the OKC level. Find him and he will
become available in both Session and 2 player modes)

Unlock Elvis outfit for riders         Circle, L1, L1, Up, Up
Unlock Kid's street bike
(for all riders)                       X, Left, Left, L1, R1, Left

     The  bike  is found in the Chicago level after you rescue the kid
with the medi-vac chopper

Unlock Las Vegas in Road Trip mode     Square, R1, Left, L1, Right,
                                       Square
Unlock Boston in Road Trip mode        Square, Up, Down, Down, Up,
                                       Square
Unlock Chicago in Road Trip mode       Square, Up, Triangle, Up,
                                       Triangle, Square
Unlock New Orleans in Road Trip mode   Square, Down, Right, Up, Left,
                                       Square
Unlock Los Angeles in Road Trip mode   Square, Left, Triangle,
                                       Trianlge, Left, Square
Unlock Portland in Road Trip mode.     Square, X, X, Triangle,
                                       Triangle, Square

Unlock all music tracks                L1, Left, Left, Right, Right,
                                       Right, X, X
Unlock ''Big Ramp'' video              R1, Up, Down, Left, X, X, X, R1
Rick Thorne FMV                        R1, L1, Right, R1, Left, R1
Seth Kimbrough FMV                     R1, Up, Up, Circle, Circle,
                                       Circle, R1
Unlock ''Day Flatland'' video          R1, Circle, Left, Left, Square,
                                       Right, Right, R1
Unlock all Cory Nastazio videos        R1, Square, Circle, Circle,
                                       Sqaure, Square, Square, R1
Unlock all Joe Kowalski videos         R1, Up, X, Triangle, Down, R1
Unlock all Kevin Robinson videos       R1, X, Triangle, Down, Up, R1
Unlock all Mat Hoffman videos          R1, Left, Circle, Left, Circle,
                                       Left, R1
Unlock all Mike Escamilla videos       R1, Circle, X, X, Circle, X,
                                       X, R1
Unlock all Nate Wessel videos          R1, Down, Triangle, Circle,
                                       Down, Triangle, Circle, R1
Unlock all Rick Thorne videos          R1, L1, Right, R1, Left, R1
Unlock Ruben Alcantara videos          R1, Square, Circle, Circle,
                                       Square, Square, Square, R1
Unlock all Seth Kimbrough videos       R1, Up, Up, Circle, Circle,
                                       Circle, R1
Unlock all Simon Tabron videos.        R1, L1, L1, R1, L1, L1, R1 
Unlock Big Ramp FMV                    R1, Up, Down, Left, X, X, X, R1

Hints

Unlock Volcano:
     Beat the game by completing all of the objectives

Unlock Day Flatland Video:
     Choose  Session  and  select 2 minutes, then choose Day Smith and
score at least 250,000 points

Unlock Mime:
     Complete every Gap

Unlock Vanessa In L.A.:
     On top of the brick building you will see a girl sitting down. Do
an  adrenaline  trick  in  front  of  her that worth 20,000+ points to
unlock her

Unlock Day Smith In OK City:
     Go  up  to  the ramp that you put in place with the fork-lift and
into  the  secret  garage. Grind on the black box, and it will open up
into  a  vert ramp. Use the ramp to grind onto the bullhorns, and jump
into the small room.

Unlock Bigfoot in Portland:
     Get  across the river and perform an adrenaline trick between the
two kickers at the bottom of the hill. There is a camera between them.
Bigfoot will appear.