An interesting Beta app from ESRI via the MapMPG web service. The application enables the user to select 2 makes of vehicles in order to compare the mileage that is expected. For example, I selected a 99 Dodge Van which is expected to get 14 mpg, then compared to a 2008 Chrysler 300 which gets 18 mpg. then the cool part, the service goes out, retrieves my location (approx) based on the ZipCode provided and returns a map showing a bounding area that you can drive on a gallon - the two polygons are color coded according to each vehicle... very cool! See it at www.mapmpg.com.
Notice the light yellow polygon showing the driving range of the 2008 Dodge as compared to the 1999 vehicle.