If anyone finds themselves in South Dakota, I highly recommend a trip to Badlands National Park. If you can catch a summer thunderstorm in the process, you're in for a pretty awesome experience.
Thunderstorms over the Badlands by David Gevert, on Flickr
Dramatic Skies over the Badlands by David Gevert, on Flickr
These are gorgeous!!! I drove through the badlands on our way to Yellowstone two years ago. I still can't get it out of my head. Must. Go. Back.