My favorite near the Badlands is the Prairie Homestead.... it is off of I-90 on 240, east of the Badlands. It is not time consuming but it is a prairie homestead... dugout with wood addition, prairie dogs, etc. It looks like the people just left yesterday. I have been several times, with different friends, and I still enjoy it. I do have to say it was better before they built the big visitors center in front of it.... with many ways to spend you money. Go thru it quickly and be transported back to homesteading life.
Enjoy the pigtail roads in the Black Hills.... Custer is great, Mammoth site incredible, and don't forget Needles Parkway.... Then not too far depending on your direction is Devils Tower and southwest is Guernsey, Wy with the Oregon Trail wagon ruts and signature rock... and Fort Laramie..... I will stop there! Oh and you will see signs for Wall Drug in Wall, SD... it's a tourist trap but it's definitely different!