Last year when I was in Vegas I visited the Neon Boneyard, and we returned again this year. I throughly recommend it, and it's even better than last year due to their new visitor centre. You must pre-book so do check it out online!
You get a tour of the vintage neon signs, which is a small history of the crazy town of Las Vegas!
It's super hot so make sure you have your sunblock, over here they sell factor 75 and 100!