I find RV Park Reviews to be quite helpful. The map feature gives me a good idea of the overnight options near my preferred stopping point on longer trips, and the the search function lets me see the options at my destination, and/or select possible future destinations that have good campground options.
The state pages give you a pretty good idea of the options in your own state, or others that you plan on visiting. My pet peeve is that RV Park Reviews doesn't let you search by rating (like Amazaon) or even type of campground, but if you like State Parks, just type "State Park" into the search for a particular state, and you'll see how the state parks in that state are rated. Unfortunately, getting the info on all the city or county parks isn't that easy.
EDIT TO ADD: I try to review most of the campgrounds I stay at within a day or two of leaving, and put considerable effort into it - more than just a couple of sentences.