I have an 09 Crew Cab, 5.7, with short bed and 4x4. Just got back from vacation and averaged out to 21 mpg going 75 mph most of the time when on the highway. So I figure that is pretty good with 5 people and the bed loaded to the rails.
I am on http://www.ramforumz.com, they seem to be a pretty good place for info on all the Ram models.