I saw the promotion advertised on tv yesterday from Mcdonald's. Every Mon & Wed hamburgers are 49 cents and cheeseburgers are 69 cents. Not sure if it's nationwide, but this was advertised in the Florida market.
Didn't catch the end date of the promo, maybe someone else knows?
(I guess this explains why when I was there this past Monday someone in front of me ordered 14 cheeseburgers)