There are a number of companies in the United States that offer cash in exchange for unused gift cards, including Raise and Cardpool. These services can be accessed using either a web browser or a downloadable app for mobile devices.
Users of these services can sell gift cards of any value as long as the card still carries a balance. However, the money they receive is not equal to the amount on the card since the company acting as an intermediary takes a cut out of the total. The gift cards sold through these services are then resold to new buyers.