One of our readers, Sice, points out that you can purchase Home Depot gift cards at http://www.skymilesshopping.com and earn miles.
He purchased a $300 gift card for an upcoming Home Depot purchase and the 900 miles posted immediately.
From the Home Depot T&C
The world’s largest home improvement specialty retailer and the second largest retailer in the United States.
Not eligible on Installation Services and on purchases made with third-party partners where the customer is leaving the homedepot.com web site.
Eligible on the purchase of gift cards. Not eligible on purchases made to buy a gift card using a gift card.