We got very lucky earlier this last August when we managed to find a campsite near Yellowstone. I didn't expect too much because everything was booked. However, we got five nights at Rainbow Point Campground, 5 miles north of West Yellowstone and loved it! It's beautiful, has very spacious camp sites, very clean vault toilets, on a lake, the quietest campground I've ever stayed at and the hosts were meticulous about keeping toilets and campsites impeccable. Our campsite's ground had been raked when we arrived. As soon as a camper leaves, within minutes they are checking the site and getting it ready for the next person. It was 5 miles north of West Yellowstone and I think 2 miles on a paved road and then 2 miles on a good gravel road. $19/night can't be beat. Showers are available at the coin laundry in town.