Try the hotel web sites directly, rather than go through Expedia, Orbitz... Sometimes, they may have quick blow out sales not listed through others.
One site is
http://www.ballys.com/nevada.html where you can look at their properties (Bally's, Paris, Ceasar's...).
One place I stayed at that was really cheap was Imperial Palace, which was nothing special but very central (across from Ceasar's) and cheap. I once got a room at Bally's (central also) for $9/night through their site.