GM.com - Check out the newest lineup in the GM brand!
Cadillac.com - 2014 New Cadillac Cars, Trucks and SUV's; Promotions and Warranty information.
OnStar - Explore the world's most comprehensive in-vehicle security, communications & diagnostics system, available on more than 50 GM models.
Kelly Blue Book - Value your Used Trade-in or See your New Car Value.
CarFax - Used Car Vin Check, Auto History Check, Vin Number Lookup
Edmunds.com - Research New and Used Cars for consumer Ratings and Value
Black Book - Another great source for Valuing your New Vehicle or Used car Trade.
Wikipedia - Read about the History of GM.