Take advantage of an active market for cards that are gathering dust. By Lisa Gerstner, Contributing Editor May 1, 2012 1. Cash a card in. As much as $41 billion in gift-card value has gone unused since 2005, says research firm TowerGroup. Online marketplaces, such as Cardpool.com and PlasticJungle.com, will buy your cards -- but don’t expect to reclaim the full value. For example, Cardpool.com was recently paying $81 for a $100 Barnes & Noble gift card. You can compare how much various sites will pay for a card as a percentage of its value at GiftCardGranny.com. Sites such as Cardpool.com, GiftCards.com, GiftCardRescue.com and PlasticJungle.com will only buy cards issued by major retailers, but you can sell any card at any price on eBay or on Card Hub’s exchange.2. Donate it to charity. But first find out whether the charity will accept the card and whether there are any restrictions, such as a required minimum balance. Alternatively, you could use your card to buy items the charity collects, such as food or clothing, suggests consumer expert Andrea Woroch. At DonateMyCard.com, you can hand over any amount on prepaid and debit cards issued by American Express, Discover, MasterCard and Visa -- especially useful for leftover balances of a few dollars or less. Choose from a list of participating charities, including the National Kidney Foundation and the National Park Foundation. The site takes a 30% cut of donations of less than $10 and 20% on other amounts. 3. Get off the ground. Airline travelers may find a new option enticing. United-Continental’s MileagePlus Gift Card Exchange allows members of the airline’s frequent-flier program to trade in gift cards from more than 60 retailers for miles. Cards must have a balance of at least $25, and you may redeem partially used cards. Depending on the market rate for the card, however, you may get more miles per dollar by buying the miles directly. 4. Look out for bum cards. Gift cards displayed on open racks in stores are vulnerable to theft, says Dave Jones, chief executive of GiftCard.com. Someone could copy the card number, then check frequently to see whether there’s money loaded on it; as soon as a balance appears, the thief makes a purchase. Call the retailer to ask whether you can register your card. That way, you’ll be able to retrieve the balance if the card is lost or stolen. And before you transfer a card to someone else, make sure the money hasn’t vanished. GiftCardGranny.com’s Balance Checker has phone numbers and Web sites for checking card balances for more than 300 stores. Advertisement 5. Watch the deadlines. Per the CARD act of 2009, retailers may charge an inactivity fee after a gift card has been dormant for more than a year. You have five years from the date the card was activated or loaded before the money expires. Any other fees must be clearly printed on the card or its packaging.