How about Glacier and the Tetons, a week at each might be enough time see all. Then from Yellowstone, if your interested just south of Cody Wy is a small town called Thermopolis and if your interested in fossils/dinosaurs, the Wy Dinosaur Center is there and they offer tours of digs that is really interesting.
You could blow a couple of weeks in South Dakota and still not see everything. Would suggest camping in the town of Custer, as it is right in the center of things. 20 minutes to Wind Caves, Custer State Park, Mount Rushmore, etc.... and then the Badlands cant be missed and if you like touristy stuff, Wall Drug will make you smile. And then there is Utah. You could spend a year in Utah and not see it all/
