More Drivers:
Enter 'Extra Drivers' as a name in Create a Car mode.

Unlock Dale Jr.'s Oreo and Nilla schemes:
Beat the Steve Park Thunder Challenge.

Unlock Tiburon Speedway:
If you have a save from any 2003 EA Sports game on your memory card, the Tiburon Speedway track will be automatically unlocked.

Thanks to Revolution readers n8zaso, TheWho333, Michael, Matt, Gordon Fan 24 and Corn_Phlake!