Cheat mode: 
At the Main Menu, enter icancheat to enable cheats. Now enter the following codes on the
specific screens: 

Main Menu:

clipped         No clipping mode
reckless        Reckless mode

Track selection:
                              
freeride        More tracks 
freedrive       Even more tracks  
lapset          Set number of laps
                     
Car selection:
                           
redfury         Jeff Gordon's car
takemeon        Expert mode
widebodyopen    Xwave car
wildone         Wraith car