I had good luck with the Edmunds.com buying program. Chris likes TruValue. You might also try the kbb.com (Kelly Blue Book) and any other that you might find. The nice thing is that you can get several quotes and choose based on both price and dealership.
Edit: Of course, you have to know what make, model and options you want before you can take advantage of a web-based buying program. You can research those things at the aforementioned sites. You can also get different cars and option combos if you want.