GasBuddy

It’s difficult sometimes to know where you can find a particular gas station or to get the best price possible, but the application GasBuddy can take care of this problem.
 
GasBuddy is a community-driven application, which means that the data is provided by other users of the same app. This means that busy areas like cities have the best information about prices and locations.
 
Users are encouraged to report the gas prices with points and achievements, and they even get the chance to win $100, through a contest that takes place every day.
 
The only drawback is that gas prices are only available for USA, Canada, and Australia.