I've said before that 90% of casual travelers are better off crediting Delta flights to an Alaska Airlines Mileage Plan account, rather than a Delta Skymiles account. For those who stubbornly persist in pursuing Medallion elite status (for example, to enjoy free award changes and redeposits with Platinum or Diamond Medallion status), Hilton has brought back a promotion from last year whereby you can earn 250 Medallion Qualifying Miles for each 2-night stay between September 30 and December 13, 2013 (up to 10,000 MQM).
You have to register for the promotion here, and select Delta as your "double dip" earning partner in your Hilton HHonors account. In my experience stays are credited according to the earning preference you have selected when you make the reservation, rather than your earning preference at the time of your stay.
Since any MQM you earn in excess of your Medallion status will roll over to 2014, there's no reason not to take advantage of this promotion if you have any 2-night Hilton stays planned during the promotional period. You'll also earn double Skymiles for stays completed under this promotion.