This holiday season should be a crazy time for gift-card exchanges, where users can unload unwanted cards. And one of those exchanges, CardPool, just added a novel way to pay you for those cards: with Facebook Credits.

CardPool makes money by buying gift cards off users at a discount, then reselling them. For example, if you’ve received a $50 gift card at a store that you’ll never shop at, you could sell it to CardPool for $40, then CardPool could sell it to someone else for $45. You can also trade in your gift card for an Amazon.com card.

So why would you want to receive payment in Facebook money (Credits are used in Facebook applications like FarmVille) rather than real cash?

Well, you might be a FarmVille addict. And even if you’re not, founder and chief executive Anson Tsai said Facebook Credits remove one of most annoying steps of the exchange process. With any other gift card, you’d have to mail it in to CardPool, then wait for the check. With this program, you just enter your gift card number in CardPool, and you get your Credits right away.

Tsai said he’d like to expand the “no mail” option to other payment types, but CardPool still needs to figure out how to avoid fraud.

“Facebook is a great start because we use Facebook Connect as a way to authenticate users and hopefully keep out the bad guys,” he said.

CardPool was incubated by Y Combinator and has raised funding from angel investors including StubHub founder Jeff Fluhr, PayPal cofounder Max Levchin, and Zappos chairman Alfred Lin.