There are a couple of places where you can trade gift cards for gift cards.
One of the best ways to find out how this all works before getting started with exchanging your card for cash, or for other cards, is to read all about the procedure in this fine Plastic Jungle Reviews article over at Premium Blend Media.
In the article mentioned above it also tells you how rather than swapping one card for another you can also get cash for it instead. It is a pretty neat procedure.
There is quite a bit of similar information about the procedures and how these companies go about making their offers in another article over at the Net Shop Manager with the title Buy Sell and Exchange Used Gift Cards.
Don't let the title fool you though. The gift card does not have to be used. Obviously no one is going to give you money for a gift card that does not have a balance on it. What it means is that they will make you a cash offer for whatever balance you have left on the card.
You can of course exchange a brand new gift card for another brand that you want as well. You don't have to get actual cash.
Don't expect them to offer you $100 for a card with a $100 balance either. They do have to make money somehow. Depending on what kind of card it is, and who it is from, you can expect to get anywhere from 70 - 95 cents on the dollar for it.
If you are doing an actual exchange of cards then you might even get a little bit more, but it all depends.
You can find out all about the procedures and what your gift card is worth by clicking the Plastic Jungle banner just below. They make it real easy to trade your gift cards for other gift cards. Check them out.