I recently discovered that Discover Card is now offering 5% Cash Back on Hotel Stays at Marriott. To take advantage of this offer you have to log into your Discover Card account online and then proceed to "Shop Discover". From there you will find a link to Marriott's website where you can make reservations as usual through your Marriott account with your Discover Card. Within 8 weeks after your stay you will receive the 5% Cash Back. See the screenshot below for the full details.
The 5% Discount offer is also valid for these Travel Companies: Dollar Rental Car, Enterprise Rental Car, Expedia, Orbitz, Thrifty Car Rental, and Travelocity.
Personally I will continue to use my Chase Marriott Card for my hotel stays as I prefer points. However I do plan to take advantage of the Discover offer for Rental Cars.
Screenshot from ShopDiscover: