Cars

Speedway Reversed bonus track

At the main menu, hold L and press X, Square, Triangle, X, Triangle, Square to unlock the Speedway Reversed bonus track.
Mirror Cup

Collect all postcards in the Postcard Rally races in Story mode to unlock the Mirror Cup.
Race as Bosses

Defeat DJ, Snot Rod, Wingo, Boost, or Chick in their Boss race in Story mode to unlock them.
Race as Doc Hudson

Win the Gran Prix Cup 1 to unlock Doc Hudson.
Race as Flo

With the Gran Prix Cup 1 to unlock Flo.
Race as Sheriff

Win the Gran Prix Cup 2 to unlock Sheriff.
Alternate paint jobs

Finish in first, second, or third in Time Trial mode on the indicated track to unlock an alternate paint job for the corresponding car. Note: You will unlock a different paint job for finishing in first, second, and third, for a total of three different paint jobs for each car.
Chick: Speedway track
DJ: Radiator Cap Run track
Doc Hudson: Mesa Ravine track
Lightening McQueen: Figure 8 track
Luigi: Diesel Forest track
Mater: Desert Canyon Dash track
Sally Carrera: Radiator Springs track
Sarge: Frank's Field track
Sheriff: Ironhorse Junction track
Snot Rod: Turbine Canyon
Wingo: Interstate track

Shortcut in Turbine Canyon

The first shortcut is found where there is about five or six obstacles. Jump or drive over them.