The site many of us use
http://www.rvparkreviews.com/. When looking at the reviews, read "between the lines". That is if you see 10 good reviews and one bad one, what were they complaining about? Do the complaints seem realistic or where their expectations too high?
We typically will not stay at any place that's not rated at least 8 or above. 7 is rated as "good" but we've found through experience that 7 really means mediocre.
Yes, I've posted reviews. I figure people helped me out by posting, I return the favor.