I've just recently started doing this. Mostly looking at places that I shop regularly. The majority of my miles are with Delta and I use the Delta Platinum Amex. For example, we always buy our pet food and supplies at PetSmart. PetSmart is part of SkyMilesShopping and offers 2 miles per dollar spent. The Delta Amex tags on an additional 1 mile per dollar. If I spend $100/month at PetSmart and I use my Delta Amex I'm only earning 100 miles. If I buy the $100 gift card, PetSmart will ship it for free and purchasing it with my Amex earns me 300 miles.

Unfortunately, many of the SkyMilesShopping partners call out specifically that Gift Cards are not included. Which is too bad because I would definitely give my patronage to more partners if they allowed this.

One way around this was by utilizing the partner GiftCertificates.com. However, they recently tacked on a $6.95 fee for purchasing gift cards. Ouch. I won't be buying from them any longer.

Fortunately, my local grocery chain sells a wide variety of gift cards for many different retailers and restaurants. And the Delta Platinum Amex offers always double miles at supermarkets. So this is at least an option for getting double miles on more purchases.

How are the AA & United programs with their affinity credit cards and partners in getting double or triple miles?