We took a trip to Custer State Park & The Badlands four years ago, and it's a trip that we'll never forget.
I know that you plan on going to The Badlands, Mt. Rushmore and Crazyhorse Monument, and we did all of those as well. They are all essential.
On the way into the Badlands is a prairie homestead that is worth checking out. You get a sense of what living on the prairie was like, and there are prairie dogs all over the place as well.
You should check out the State Game Lodge (we stayed and had breakfast there). They have a Buffalo Safari Jeep Tour that is great. It was the first thing that we did, and I highly recommend it. When everyone else went to bed, Ellen, Luke & I went for a night drive on the Wildlife Loop (I recommend at least one day and one night drive) and a herd of buffalo crossed the road right in front of us. The stars at night are awesome, the best I've ever seen.
The Needles Highway & Iron Mountain Road are worth the drives. Awesome scenery including cool views of Mt. Rushmore through tunnels along the way.
We hiked two trails there and that was a lot of fun.
The Circle B Chuckwagon dinner & cowboy music show is excellent. They have a gunfight in the street before dinner, and they put on a good show. There is horse trail riding there as well, but we didn't do that because of lack of time, but I hear it's great.
We visited the great Adams Museum and the Mt. Moriah Cemetery in Deadwood where Wild Bill Hickok is buried. There are several gold panning museums, but we went to the one in Lead, and everyone had a great time there. There are lots of local historical things there in addition to the gold panning.
You definitely should stop in at Wall Drug, it really is as cool as everyone says.
If you pass through Mitchell, The Corn Palace is interesting, but I wouldn't make a special trip just to see it.
Here are some Links:
http://www.allblackhills.com/badlands/prairie_homestead.php
http://www.custerresorts.com/state-game-lodge-custer-state-park-resort/things-to-do.php
http://www.circle-b-ranch.com/
http://www.adamsmuseumandhouse.org/museum/overview.html
http://www.deadwood.org/OfficialGuide/AttractionsTours/MountMoriahCemetery/
http://www.southdakotabeautiful.com/western-south-dakota-tourism/34-black-hills-mining-museum-lead-south-dakota.html
http://www.walldrug.com/
http://www.cornpalace.org/
