Where to Find Open Textbooks for Free:
"A growing number of online students are able to download their textbooks for free.
Many professors are beginning to teach from open textbooks, instead of requiring students to purchase pricey materials. Open textbooks are often written collaboratively and always give students legal permission to use the material at no cost.
There are several places to download textbooks online, but it's important to choose a site that offers these materials with the author's permission in order to avoid legal trouble. Consider established sites such as WikiBooks, Connexions, OER Commons, MERLOT, and the Community College Open Textbook Project.
If your textbooks aren't available in open format, see: How to Find Your Textbooks for Cheap or Free. "