Use the following two to get an idea of how much a car (used or new) is worth.
Edmunds - discover, price and buy the car that is right for you. Kelley Blue Book - the trusted resource for pricing new and used cars.
Cars.com - Browse and search for cars based on the specifics you want. Links to cars available for sale. US News and World Report Cars - Car, SUV and Truck reviews and rankings. Helpful reviews on all makes and models. Top Gear - entertaining reviews of various cars from the BBC. Alex on Autos - home of the most detailed car review videos online. If you want honest reviews with no antics, plenty of pricing and comparison details and a detailed tour of the interior, then this is your stop! Also has a great youtube channel. CNET Roadshow - has a helpful "shop for cars" and "best cars" sections when you are just browsing or looking to buy.