Intellichoice has prices, best overall values, used car valuation, comparisons, rebates, etc. AutoSite has reviews, comparisons, used car valuation, new car incentive programs, recall alerts, etc. CarSmart has a great payment calculator that instantly adjusts the payment as you move sliders to adjust the rate or payback period. AutoByTel has pricing information on new cars as well as a certified used car program which claims to find you a car in 72 hours.
Site also includes financing, leasing, and insuring info.
Autopedia has links to sites that help with all aspects of car buying including a site on tire reviews. AutoWeb lets you sell your used car, finds a new car for you, and lets you price options. Pricing is not very accurate according to press. PhillyNews Auto Page has new cars, used car evaluations, ads, etc. National Highway Transportation Safety Administration has info on safety problems, test results, etc.