- Crazy Horse Memorial (not part of the national park system) - just fantastic, and cool to see a work in progress
- Mount Rushmore National Memorial - nice hiking trails
- Sturgis - lots of biker-themed stuff, most significant town in the area before Rapid City
- Wind Cave National Park - I haven't been there, but heard good things
- Bear Country USA (Rapid City) - a park where you drive your car through pods of bears, elk, wolves, etc. Can get some great pics!
- Wall Drug - kitschy town with old west theme - amusing stop on I-90 about an hour east of Rapid City, near the Badlands
- Badlands National Park - incredibly surprising and dramatic, watch out for sudden windstorms
never stop learning!