Take a detour through Lake Mead park for the scenic route to the Hoover Dam. Sure it costs $10 bucks, but it's a lot more interesting than the freeway.
If you're feeling adventurous take a turn off the main road in the park and drive down to Lake Mead. From there you can really see how far the water level has dropped over the years. I saw several people taking in the beach although I thought it was a little too rocky to really enjoy a good walk or swim.