I have three useful websites for books.
www.audible.com - For a fairly cheap price you can download audio books. I like this b/c I like to run and knit while I listen.
www.paperbackswap.com - You can exchange books for free with other people. Every time you give a book to someone, you get a point. Anytime you receive a book, you lose a point. You do have to pay for shipping but the idea is that it will be made up when someone ships a book to you.
Lastly, your local library website. You can get audio books, regular books, movies, and music all for free. Often you can reserve a copy, look for items in the online database and renew your checkout on the website. Even if a library does not have a book you can have it shipped from another library. I know on my libary's website I can even download audio books online. I'm trying to get into the habit of using them more often b/c it will save me lots of money so make sure you support your local library because it is a great resource.