I don't know about you, but there have been many instances during our eighteen month trip around the US, and after, where we have been sadly disappointed with a campsite. Maybe it's that the facilities don't match what is promised, but often it can be more subtle things like there are only two washers and dryers and one of them is broken, or that they charge $2:00 per load, or perhaps it's that they do have a hot tub but it's never heated (one of my pet peeves).
About half way through our trip we stumbled across RV Park Reviews (www.rvparkreviews.com) which we found to be very useful indeed. What I like is that not only does it give you all the usual information like number of sites, price, facilities etc, but also honest and frank reviews by fellow RV'ers, for example:
"If you are desperate and want a bargain, I guess this place is OK." or
"I was wondering why this was the only RV campground available in May for reservations over 4th of July. This has to be the least nicest RV campground we have seen over the last month of our summer trip. The only things positive about this yucky campground, was my gravel site was level..."
Check it out, and if you like it, don't forget to leave your own reviews, it all helps!