Oh I like this one and if you are NOT mileage running in Sept this year there is something wrong with you ;-)! This one can work from ORD or MDW for the same price and is wide open weekdays or some weekends. Here are the numbers:
4,962MQMs at under 4.9CPM
Bookable on Delta.com
DM yields a very nice 11,166 Skymiles per CWSI.net!