"It turns out you can sell unwanted gift cards for up to 90 percent of the card's value," said Lisa Lee Freeman of ShopSmart.
ShopSmart checked just how much you could get at each of the sites for a variety of gift cards including Applebee's, Bath & Body Works, Gap, Kohl's, Macy's, Payless, Pier 1, and Wal-Mart. For a $50 Gap card, prices ranged from $32.50 to $40.
"We found in our search that Wal-Mart's card was the most valuable," Freeman said.
However, there wasn't a site that always had the best deals, so you've got to shop around. These sites will also let you buy gift cards at a discount.
"You could pay just $40 for a $50 gift card. That's $10 saved right there, but you have to be careful," Freeman said.
When buying a gift card, be sure to look for a guarantee on the site.
"If the site doesn't have a guarantee, you could be out of luck if the card turns out to be invalid or if it has less than the advertised value," Freeman said.
And don't lose that gift card. You won't be able to replace it because you won't have a receipt.
The government is also getting ready to help people who've got gift cards they haven't used. In August, new federal rules will make it illegal for gift cards to expire within five years after they've been purchased or reloaded with additional funds.