Through April 25, American Express Platinum cardholders can get two free nights at either the Wynn or the Encore in Las Vegas. Apparently the stays come with full Fine Hotels & Resorts benefits, which means you receive a $40 breakfast credit per person per day, one free lunch per stay, a room upgrade, and 4PM check-out. There are certain blackout dates. Mention the code E1320401 to your Platinum Travel Concierge. More details can be found at DansDeals.com.
(Tip of the hat to Raj for sending me a link)