This web site is the first place to check whenever you are doing any RV travel. I find the postings fair and quite complete. There does not seem to be a great deal of flaming, except a common complaint of grumpy checkin staff. Apparently the RV park industy does not value customer service, at least based on my observation of reviews.
This is also a good site to find alternatives, it is based on state and city but then will give you the option of checking on nearby cities as well. It is not complete, some places never show up for review but it is the best I have found.
Aother tool I use alot of is: www.tripadvisor.com
what a great tool for restaurants and lodging, surprisingly campgrounds appear as well. The campgrounds are usually larger ones such as in National Parks. For instance they cover Coulter Bay RV Park in the Grand Tetons.
Tripadvisor is available as an app as well, I use it while traveling on my iPhone.