I knew very little about the Hoover Dam before embarking on a family trip here a couple days ago.
We splurged on the "Dam Tour", which included entrance to the Visitor Center, a short 10 minute movie about the dam, and a guided tour through the turbines, generator room, and a few other top secret tunnels. This all access tour is $30 per person and is probably worth the extra $15 per person.
Visitor center is a pretty good museum about the Hoover Dam, from the developing water crisis in early 1900s to construction to the process by which power goes from running water to electricity for our homes. Lots of photos and blurbs...you'll probably want at least 30 minutes in here.
The tour guides did use gratuitous "damn"/"dam" jokes, but they also gave good info that wasn't conveyed in the movie/exhibits. They take you deep into the bowels of the dam, and you have the opportunity to look out one of the vents on the face of the dam.
One suggestion: HOLD ONTO YOUR HATS -- I saw a few hats go flying off the observation deck with gusts of wind.
Probably won't ever go back, but I'm glad I saw the damn Dam