Place an ad on Craigslist.com and social networking sites requesting specific books to use for your classes. Sometimes, when bookstores stop buying back older editions of books, students are left with textbooks they no longer need. Even though it may not be the most current book, you may be able to swap with other students or purchase the books from them for cheap.
Check your library or an inter-college library catalog for textbooks used in class. You can request books through your college and wait for them to arrive at your library. Throughout the semester you can renew the book until the semester is complete.
Look for an eBook version of the text. If you are taking a classical literature course, you may find free downloads of the books you are reading for your class. Some publishers may also offer free downloads of specific chapters of books. In other cases, physical books may come with discs or a code for electronic downloads. You can ask a classmate to give you this code to download the electronic version for free.