Press Down, Up, Left, Down, Right, Up, Square, Triangle at the title screen.
Unlimited Crew Charge:
Press Down, Up, Up, Right, Left, Left, Right, Square at the title screen.
Press Left, Up, Left, Down, Left, Down, Right, Square at the title screen.
Press Down, Right, Right, Left, Right, Up, Down, Square at the title screen.
Unlock NFS:C Vinyl:
Press Right, Up, Down, Up, Down, Left, Right, Square at the title screen.
Unlock Cardboard Box and Driver Vinyl:
Press Up, Up, Down, Down, Down, Down, Up, Square at the title screen.
When you have a drifter on you crew, set them active. Then in the race get in the air-stream and and use NOS. They have to keep a certain distance between them and you, so if you go faster they will to. I used this in speedbreaker races and won every time. Note: this is good to use with unlimited NOS and unlimited crew charge.
(supplied by: master)
More money per race:
You must have Samson in your crew for this to work. Set Samson as active, as he will give you 10% extra cash each race. Keep Neville in the crew but do not set him active. Now for each race you will get 10% extra cash per race AND $200 extra cash from Neville. For example, after one race you would normally get $18,000. But because of Samson and Neville you get an extra $200 and an extra $1,800 (10% of 18,000). So you get $20,000 instead of the normal $18,000.
(supplied by: Chingy42007)
Driving without X:
If you are driving on a long straight road while holding X, let go of X and click R1 quickly. Then use NOS and you will be driving without holding X. This doesn't increase your speed but it's still a cool glitch that you can use. Once you hold on X again your speed will go up rapidly.