What are some good online textbook sites?

Course Smart and Bookbon.com are good websites that carry online textbooks. On Course Smart, users can buy electronic versions of textbooks for up to 60 percent less than the price of a printed textbook. The website features textbooks in many categories, including biology, management, social sciences, humanities and world languages.

Bookbon.com has free textbooks in PDF files. The books typically contain only the most important facts, and most of the textbooks are 50 to 100 pages long. Most of the books on the website focus on accounting, IT, economics, engineering and management. Other available subjects include law, languages, natural sciences, statistics and marketing.