What is there to do in the south west US?

My mom wants us to go on a road trip . We're going (driving) from Atlanta to Little Rock, Oklahoma, Albequerque, Pheonix, San Diego, Los Angelos, Las Vegas, Salt Lake City, Cheyene, Lincoln, Kansas City, St. Louis, Luoisville and back home. Please tell me ANYTHING we can do along the way at at our stops. We'll be on the road for a month so feel free to tell me what ever. FYI I know we're already going to the Grand Canyon, Hoover Dam, Hollywood, and San Diego Zoo. Any recemondations and tips would be greatly appreciated. Thanks!