Did you get a gift certificate or gift card for the holidays? They've become quite the mainstay for folks who want to give something a bit more meaningful and festive than cash. But they can be the gift you'd rather not have. An L.L. Bean gift card doesn't cut it for a fleece hater; the Williams-Sonoma card doesn't do much for the non-cook. Maybe you'd just rather have the cash? Maybe you've got a pile of expired gift cards you're always forgetting to use and hate the thought of adding another one?

Whatever the reason, there are a bunch of places on the web where you can buy, trade, swap, and auction gift cards and certificates. Typically, a card or certificate sells for a little less than the face value of the card. So, for example, a $50 Barnes & Noble certificate might be listed for $45. Typically, there's also some sort of transaction fee, usually for the seller. Sometimes it's a fixed price and sometimes it's a percentage of the transaction.

Here are some of the sites I stumbled across as the subject of unloading unwanted certificates came up over our holiday.

CertificateSwap lets you register and list your certificate for free. When it sells, there's a 7.5 percent processing fee for the seller.

Cardavenue lets you buy and sell, but you can trade or auction too. The auction is handled much like an eBay auction. CardAvenue takes 3.9 percent of the transaction. If you want to trade you can specify what card you'd like to trade for and they'll notify you.

Gift Card Buy Back will simply buy your card from you for a percentage of its value, and it lists the percentages it'll pay. Then it lets you buy a gift card as much as 20 percent off of the face value, so it all evens out.

Swapagift.com offers immediate cash for your cards and posts a list of how much it'll pay (anywhere from 60 to 75 percent of the value on the card seems to be the average). Or you can pay a flat fee of $3.99 and sell your gift card directly to another site user.

GiftCardBazaar, like Swapagift, buys your card for a straight 68 percent of its value or will give you a credit toward buying another gift card from their site at slightly better rate.

Two great blog posts that do a good job of covering the re-gifting certificates territory come from ProBargainHunter and The Tao of Making Money.

Be forewarned. There are plenty of ways to get scammed when buying and selling gift cards. After all, you're buying a piece of plastic that's like cash, only you have no way of verifying what's on the card until you go to spend it and you face things like expiration dates. The FTC offers some cautionary advice for using gift cards.