I found this sweet site that allows you track your mileage and compare.
http://www.fuelly.com/It's about time we look at "real world" mileage and bury the EPA estimates, because they are almost always optimistic.
Also very useful for passenger truck mileage because that isn't usually published. If enough people get wind of it, it could have a real impact on manufacturers through demand based on true, and not only advertised economy.