The E-Books Directory is a great resource for teachers and students. It contains links to thousands of free e-books, including textbooks, that can save schools money. Instead of purchasing textbooks, and then worrying about damage and loss, schools could use e-books instead. I have only reviewed the science books and there are a lot of really good e-textbooks listed here.
Give it a look. Even if you don't use an e-text as your primary book, your students could use them as references and for extra help.