Officemax currently has an unadvertised deal for $15 off $300 or more in Mastercard gift cards. Since Office Depot does not sell Mastercards, this deal appears to be available at Officemax only.
Save $15 instantly with the purchase of $300 or more in Mastercard gift cards from 8/2-8/8/15.
Limit 1 per household/business
This deal should combine well with the recent Amex Offer, although I have had mixed success with splitting payments at Officemax.
For more info about setting the pin and liquidating these U.S. Bank issued Mastercards, see: Beginner’s guide to buying & liquidating Visa & Mastercard gift cards