Buying a car: Looking for a helpful website

[Moneyline]

Does anyone know of a website or other resource that compares gas mileage and other important factors of used cars. I'm mostly looking at American cars because they tend to depreciate in value faster than foreign ones, but I know almost nothing about cars, and could use a little help in determining which model I want to buy.

Also, are there any Vegas residents who can recommend a mechanic that works on American cars (I live just east of the center of the strip).

Thanks...