Cars (GC)

Cars cheats:

Avoid Getting Lost
If you ever get lost in the desert, follow Mater or any other car without bumping into them. They will take you back to Radiator Springs.

Cheat Mode
Enter in cheat Menu:

All Cars - YAYCARS
Hard Story Mode - CHMPION
Fast Start - IMSPEED
Unlocks all tracks and mini games - MATTL66
Unlocks all tracks and mini games - IF900HP
Inf Boost - VROOOOM
Unlocks Art - CONC3PT
Unlocks Movie Clips - WATCHIT
unknown - R4MONE
Unlock Master's Speedy Circiut and Master's Countdown Cleanup - TRGTEXC

Lightning Bolt
The first stripe (near the fire house) of the new road is actually a lightning bolt.

Sinking Cars
In Story mode, go to Ornament Valley. Follow the train tracks until you get to the big curve. Wait for a car to appear then drive into it. The car's wheels will sink into the ground and it will not move. If you hit Sarge's front he will sink into the ground and will not be there any more.

Other Sites you may consider
CheatServer.Com
Cheat Codes Club