This is one of the coolest sites I've ever found. If you regularly give gift cards as presents or maybe you have a whole bunch piled up that you never plan to use, check this out.
Two great sites: Giftcardgranny.com and Giftcardrescue.com. Both allow you buy and sell gift cards to big retailers like Home Depot, Best Buy, and Amazon. As well as chain restaurants, pharmacies, online stores, etc.
Now, if you have gift cards you don't plan on using, you can sell them on these sites and get cash in exchange.
photo: HerrKrueger, Flickr Creative Commons