Warmshowers.com is a great idea but it has the drawback of having to trust strangers.
Trusting (and meeting) strangers is a huge appeal of warmshowers for me. Everyone I've met as a guest and a host has been great.
As far as simple campsites for bike tourists, I wish campgrounds across the US followed the Hiker/Biker model of the Pacific Coast State Parks and had a separate little section that was cheap and simple and located away from the vehicles. (Heck, I wish the sponsor of this fine website had a simple Biker campground (on or offsite) at their headquarters in Missoula, MT. While the hospitality is wonderful when you visit, the only campground in town is a KOA.)