Red Rock Canyon is less than 20 miles from the strip and a must if you are the outdoorsy type and/or enjoy the beauty of the desert. There's a $7.00 admission fee in exchange for a map of the 13 mile scenic loop. There's a great visitors center with informative exhibits about the history, wildlife and vegetation in the park, as well as a nice gift shop. I was personally hoping to see the wild burros said to live in the park. I didn't see any, but after speaking with a nice park docent, he pointed me toward the village of Blue Diamond, a right turn and about 5 miles out of the park. I found them!
Also, if you love Red Rock Canyon, research Valley of Fire, about 50 miles north of Vegas.