[folivier]

Escapees are good, their campgrounds tend to be basic with lots of fulltimers. They have a first-in/first-out rule. So you can always get a site. But I'm not sure if they can accept 45' coaches. They do have discount agreements with a lot of campgrounds.
FMCA or Goodsam are good for 10% off at a lot of campgrounds that don't take other discounts.
We have a Thousand Trails zone pass (southwest & northwest zones) which also gives us discounts at any Encore Resort.
Definately get Passport America.
Harvest Hosts is kinda neat. We spent last night at a goat ranch. It was quiet and in the country with great hosts. You pay harvesthosts.com $40/year and stay overnight free at farms, wineries, ranches, etc.