Check out the northern part of the "Grand Circle, and perhaps Horseshoe bend and Antelope Canyon at Page, AZ. The tightest concentration of wonderful parks that I know of. Zion, Bryce, Red Canyon, Capitol Reef including Waterpocket Fold, Kodachrome Valley, Notom Road and Burr Trail Road, Hole in the Rock Road (Devil's Garden, near Escalante town, 20 miles on dirt road), Valley of Fire state park near Las Vegas is worth a stop, too. I have not not mentioned all the wonderful parks in this loop.
http://www.grandcircle.org
Also: Coast highway Rt 1 in CA, from the Morro Bay to Monteray.