GasBuddy - GasBuddy lets you search for Gas Prices by city, state, zip code, with listings for all cities in the USA and Canada. Updated in real-time, with national average price for gasoline, current trends, and mapping tools.

TrueCar - Buying a car can be painful.

Fuelio - Track your fill-ups, fuel consumption, fuel costs and save money.

CarCatch.uk - Find new and used cars for sale in the UK with CarCatch, an aggregator of all the top auto marketplaces

Fuelly - Fuelly allows you to tracks your gas mileage over time, helping you calculate fuel expenses as you drive.

Kelley Blue Book - New & Used Car Price Values