At the main menu, move the cursor over the race button. Don't click yet. Then whilst holding down shift type in the following :

1. Vwbug
2. Volvo
3. BMW
4. Semi 
5. Bus
6. Commanche

Also , at the track selection menu, type in "Hollywood" this will give you the Hollywood track.

Another little trick , try typing in "Pioneer" at the main menu and see what happens.