An interesting museum, just blocks from the Las Vegas strip, is the Atomic Testing Museum. This museum focuses on the history of Atomic weaponry in Nevada, which went on from the 1930's all the up into the 1990's. We found many interesting exhibits showing the progression of Atomic technology along with how popular culture progressed over time. For anyone with an interest in this type of history, it's definitely a great place to visit and can give you something else to do in Vegas besides the typical Strip tourist items. However, this doesn't have anything related to the standard Vegas drinking and gambling, so if that's your focus, it isn't worth the visit.
Also, temporarily, they have an exhibit called Area 51, which concentrates on the possibility of if aliens have visited Earth before. You'll get to see various "evidence" and it's definitely interesting, and amusing if nothing else.