Extra Cars, All Tracks:
When you are asked to enter your name, enter this: (just enter 1 at a time)

cheat1
cheat2
cheat3
cheat4
cheat5
ciggies

This gives you : 4 more cars, the hotrod, the monstertruck ,the 4x4 buggy and the stock-car. It also gives you all tracks and no-clipping mode.

Porsche:
When asked for you name, type in "this is awesome". You will receive and older and newer model Porsche.