I was happy to hear about the Hoover Dam but I think its the only one.
I've been sitting fooling with Google Maps for a few minutes, and it's really looking like Hoover Dam is about all there is, at least in terms of major landmarks with a chance of being internationally known. Which sort of gibes with my 30-ish year old memories of having been out there- outside of Hoover and Vegas, it tends to be "pick a direction, and look at all the desert."
Aside from smaller "more local" things like the in-game Dinky the Dinosaur, anyway- and actually the number of those sorts of things is almost staggering once you get off the Interstates and scout around.