Without a car, you won't go far. I-90 is the sole interstate in the region, running east-west, skirting Black Hills NF and Badlands NP to the north, and passing through Rapid City. It goes on to Sioux City in the east, and west to Wyoming to connect with I-25, which leads south to Denver.
The main sights are indisputably the cyclopean sculptures at Mount Rushmore National Memorial and the embryonic Crazy Horse Memorial, both of which are right by Custer. Wind and Jewel Caves, as well as Badlands National Park are also well worth a visit. But if you are here to just snap photos of a few main attractions, you are going to miss the point. This is beautiful, big, wild country, and to appreciate it, you'll need to spend days driving or hiking around to take in the glorious scenery, gawk at wildlife, wonder at the night stars, and enjoy the fresh, clean air.
Drive through "Bear Country USA", a "drive-through zoo" containing many animals you otherwise would not want to be in proximity to.
Hike or at least check out the incredible Badlands.
Ride down Highway 16, off of which are conveniently located many of the area's numerous attractions.
Tour the local highways, which can be very scenic in nature.
Visit and enjoy Evan's Plunge in Hot Springs, a mini-water park fed by hot springs.
Visit the area's most famous attraction, Mount Rushmore.
Visit the Mammoth Site
Watch the Old West Shoot-out in Hill City
Horseback riding and camping  soak in the beautiful scenery in the heart of the Black Hills.
Circle View Ranch, 20055 E. Highway 44, ☎ 605-433-5582, . South Dakota Hotels: Circle View Ranch, Hotel near Rapid City SD. Circle View Ranch offers the best and most unique view in South Dakota. Our 3,000 acre ranch is located just 6 miles from the heart of Badlands National Park and 1 hour east of Rapid City and the Black Hills.
The Alpine Restaurant in Hill City -- Dinner menu is limited: Small or Large Filet Mignon. Be sure to save room for dessert!
The Hitchrail Bar and Restaurant in Pringle -- See a true small town watering hole.
This is a usable article. It gives a good overview of the region, its sights, and how to get in, as well as links to the main destinations, whose articles are similarly well developed. An adventurous person could use this article, but please plunge forward and help it grow!