Freakin Frog is great. Lots of craft and Belgians.
There is a place called Big Dogs Brewing Company in North Vegas, not really that close to the strip but good food and decent beer.
There aren't a lot of places with good beer on the strip but The Pub at Monte Carlo is probably one of the better ones. They're have all the more common craft beers (Stone, Rogue, Dogfishhead ect.)
There is also Sin City Brewing Company, which isn't the best beer in the world but better than most of your other options in Vegas. They have places in a few of the casinos. Venician, Flamingo, and Planet Hollywood I think.