I've been using discounted gift cards to purchase items at stores I frequent for at least a year now. The savings have been really good. Not only am I getting gift cards at below value, I am combining(stacking) these savings with click-through rebate(cash back) sites, coupons, and sales.
Here are some gift card sites that I've used without any problems:
ABC Gift Cards
Gift Card Rescue
The savings vary throughout the year. I've gotten anywhere from 2%(Walmart) off to 40%(AMC theaters) off. It's worth it to keep checking back for the good deals. The values generally vary as well, so if you want a small or high value card, they'll be able to accommodate you. If the percentage is high, I go for the high value gift cards. It saves me money in the long run, and is a better rate than I'd earn sitting in the bank. The gift cards have no expiration date per law.
Here(Cash Back Chart) is a compilation of rebate(cash back) click-through sites by savings level organized by store. This is so helpful! Simply look up your store and choose the highest savings rate.
Retail Me Not is one of the better coupon code sites. Check here and Google for coupon codes to stack savings.
One of the easiest stores to apply this stacking method is Payless Shoes. They are always offering specials(like BOGO), have generous coupon codes online, and offer free site to store delivery. The gift cards are usually deeply discounted, and the cash back sites have a decent cash back rate. You can triple stack savings with current sales and take a nice chunk off your final price.