Believe it or not, most of the school libraries have the latest textbooks required by professors. Most students can go to the library and rent the textbooks out to scan or read. This not only saves students a ton of money, it is also the easiest way to obtain new textbooks that may be hard to get elsewhere.
If you want to save some money and be environmentally friendly, electronic books (E-books) are a great alternative to buying actual textbooks. E-books are becoming one of the most popular forms of reading, since people can read it directly from their iPad, phone or an e-book reader.
Unless all other options are ruled out and you must purchase a book for a class, there are actually several very useful websites that sell secondhand textbooks at a much lower rate. For an extensive list for discounted books, please check out this website: http://studenthacks.org/2008/01/23/used-cheap-textbooks/