We were just out to Grand Tetons, Yellowstone and Glacier National Parks. We stayed at Fishing Bridge in Yellowstone and I wouldn't do it again due to such small sites and mosquitos that made it impossible to sit outside at the campground. If I were to do it again, I'd camp outside the park near the south entrance and then head to the north and/or west entrances and camp near the entrances. Yellowstone is big and you have to do a lot of driving if you camp in only one spot. We left via the north entrance, and that area looks really interesting but it was so busy that we couldn't pull over with the trailer in tow. Yellowstone is great for the wildlife, but we actually enjoyed the Grand Tetons and Glacier more. If you have time, go to the Tetons as they are just south of Yellowstone. Coulter Bay (in the park) is a nice campground and a good base for seeing the Tetons. Taking the tram to the top of the mountain at Jackson Hole was amazing!
And, the South Dakota Badlands are still one of my favorite spots....been there twice and I'd go again.