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. Once you add the promo code at Orbiz.com and click on a qualifying package, you can see all the details under the Special Offer rules.
In Las Vegas, for example, the valid pacakges with the code is pretty limited. COUPON ICON must appear, once you've added the code, for it to be valid for a specific package.