ORBDOT75 takes $75 off a 3-night Hotel + Airfare stay. I found this thread on FatWallet
http://www.fatwallet.com/t/63/719389/ I have verified that the code works. From LAX-LAS, I have found a number of dates (Sunday, Monday or Tuesday departure for a 3-night stay) as low as $102 for hotel and airfare including all taxes/fees at the El Cortez Hotel & Casino Las Vegas.
EDIT: Good news. The promo code is valid thru 12/31/2007 for travel thru 3/15/2008. When you enter the promo code at Orbitz, click on a package it is good with and you'll see those details under this Special Offer rules.