I am currently using a PS3 controller plugged in via USB to emulate a 360 controller. I would like to get a wheel and pedals but I am saving for a laptop.
I used a keyboard until yesterday when I got my F310 gamepad to work. Waiting for wireless Xbox controller adapter in the mail. (less than 10 bucks on ebay) (Mostly because I like using xBox controllers for racing games better) When I was little we had a computer that the whole family used. My dad got a cheap wheel and NFS Porsche Unleashed. When me and my younger brother were playing it we figured out that if we turned too hard the wheel would keep turning. It ripped all the wires out. My dad tried to solder them back where they went but a few got mixed up so when plugged in the wheel would go all wacky. Later we got another wheel which was really cool. After the rest of the family kinda stopped using it I used it on my computer to play 18 Wheels of Steel. But that also broke. (I forget how) A couple years ago I got a free nascar wheel. (Not sure exact model) It was old. It used the gameport plug. One paddle didn't work and it had no force feedback but it was good enough for me in World Racing 2. Unfortunately, because the springs in the pedals were so strong, the gas pedal actually broke off when I floored it once. Since one of the paddles didn't work (Not shifter paddles, they had axis) one was gas and a button was brake. After a while I stopped using it and it went into the basement where I think it's broken if it hasn't been thrown away yet. Then a month or two ago I was at best buy and bought my Logitech gamepad. I also use a logitech joystick that it really my dad's but he hasn't used it in a long time. (WingMan Force3D (Pretty nice))
Keyboard, because I don't know yet if possible to use Logitech DriveFX (plastic wheel) About keyboard, some are saying it's annoying and unplayable... or something. I think this is pretty good. (only Civetta Bolide is pretty impossible to drive, but I don't really care)
You can get some cheap pedals and a steering wheel there is some Logitech ones that are easy and cheap
Keyboard - because it's easier for me to hit the slo-mo buttons and spawn cars etc. I'd maybe use a controller but really can't be arsed figuring it all out. I just want to play the game