Online there are many places were you can exchange books that you have read for ones that you want to read. This can be a great way to catch up reading in a cost-effective manner.
Book Crossing is an online free book exchange movement. It is considered the act of releasing your book into the wild by leaving it somewhere for a stranger to find. You can either put it on a park bench or track its location for another Book Crossing member to find.
Books Free Swap is a site where one pays only to receive books. The recipient pays for postage (usually $3.28 USD). There is no direct swap requirement and the postage prints instantly online. With this service, you simply get books you want online. You don't have to send books to receive them.
Freecycle Network is an organization made of over 5000 groups and close to 9 million members. It's a grassroot and entirely nonprofit movement of people who are giving and getting stuff for free in their own towns and neighborhoods. It's all about reuse and keeping good stuff out of landfills. Each group is moderated by volunteers and membership is free. The purpose of freecycle is to trade items that you don't need for ones you do need, including books.
Paperback Swap is an online book swap club, specializing in hardbacks, audio books, textbooks, and paperbacks. You join and then can swap books with other members. Once your book is requested, you just mail it to a member. In return, you are able to choose from over 1 million available books. You may pay for the postage on books you send out. The books you receive come postage paid. The books you request, you can keep or trade again.
Trade Made is a platform which lets users save money by trading items, including books, that you no longer need for other items that you do need. It is meant to influence positive environmental change. The app requires download onto a phone or computer. You then upload an item or service, including photo with some details. Then, you filter by distance, Facebook Friends, trade & save, and make a deal. You can accept, reject, or counter trades you have sent and received.
Participating in a book exchange can be a fun free way to get your hands on some new books of interest.