To find the best deal when buying a new car I use The Autoline. I can’t recommend them highly enough. For $200 they will find the car you want (or recommend the car you should buy based on your budget and requirements) and call you back with the best no-haggle price they can find. (They also do leases.) I’ve used them four times now and am very happy with the results. Each time they’ve arranged for dealer to deliver the car to my house, so I never have to set foot in the dealership or hassle with the guy who pressures you to buy useless “clear coat” and other pure profit add-ons.
Don’t be put off by their 1993-style website — all business is conducted by phone and email.
UPDATE: I just remembered that I interviewed Patrick Schallert of The Autoline for Credit.com a few years ago.