In my experience no one directory or website lists all the campgrounds, RV parks or other possible overnight or longer term stopping locations. I use the following websites to find campgrounds along our route:
RV Park ReviewsPassport AmericaAllstaysRV ParkyWoodallsFree CampgroundsFree CampsitesU.S. CampgroundsNational Forest Campground GuideUltimate Public Campground ProjectCorps of Engineers CampgroundsBob’s Cheap or Free CampgroundsDean’s ListBoondockers WelcomeHarvest HostDays End DirectoryDon Wright’s GuideI prefer the ones that show locations on a map rather than needing to know the city to search for. Several of the above websites also offer a download of their data which can be imported into mapping programs or a GPS. I find this particularly useful because I can then see the locations along any proposed route. The
Discovery Owner's Forum and
POI Factory have a large variey of downloads for GPS and mapping programs.