The Rio currently has a very good room sale going on. The rates do fluctuate, but right now they are better than the negotiated rates for a number of upcoming conferences. You get a room for an average nightly rate of $60 for one upcoming conference.
The Rio does not charge resort fees either, so the rate you see (plus 12% tax) is what you actually pay.
The offer code for the Rio is IRFNF. You can click on the following link to get to the page with the code already active.
(Dec. 10, 2012 update: The offer code is still good and is showing savings of over 50% off the regular rate for some dates)
(Nov. 7, 2013 update: The offer code is still good and is showing rates of $29 for many dates in November, December and January)