The school bookstore is usually the first place to look for your textbooks. Generally, professors let the bookstore know what books they'll be using for the semester, and the bookstore will keep a supply of new and used books based on what the professors tell them. Many people claim that you won't find the cheapest textbooks at the campus bookstore. While this may or may not be true in all cases, shopping around before the semester starts may be beneficial. You can also venture to another campus to look at their selection of textbooks. They may not have the books you're looking for, but it may be worth a shot if you are having trouble finding them anywhere else.
Half.com is a website that sells all sorts of things, such as books, music, movies and games. It is a very useful website to find and purchase new and used textbooks at potentially lower prices than campus bookstores. The website is an Ebay company, and you have the opportunity to choose from many different sellers for each book that you want to purchase. The books being sold vary in condition and price, so look at the descriptions carefully before committing to a purchase.
Campus Books is another website where you can purchase college textbooks. You simply type in the name, ISBN, author or keyword of the textbook and click "search" to find the lowest prices. It offers textbook purchasing as well as textbook rental, which could help you save lots and lots of money. There is also a local bookstore pickup option, where you can order your book online and pick it up at your school's bookstore.
Big Words is a very useful website for buying, renting and selling textbooks. Like the other sites, all you have to do is type in the ISBN, title or author to find the books you need. If you're renting books, Big Words sends you the books in the mail, and you send them back at the end of the semester. Not only is renting usually less expensive than buying books, but it also takes away the hassle of trying to sell books back when you're done with them. If you buy books at Big Words, you can also sell them back once you're done with them.