First of all, there is a web site that is called Paperback Swap. You list books that you have that are in good condition but that you don't need anymore. When someone on the site wants one, you receive an email. You send the book to them via media mail (which is a cheaper way to mail books). This usually costs between $2 and $3. Then you receive a point. You can then use that point to order a book from someone else. That person pays for the shipping of your book. When you sign up and list at least 10 books, you receive 2 points so that you can begin ordering books right away. I have gotten many books for my classroom library this way. Sometimes, if you are very lucky, you can even find some teacher books on the site.
Another place that I found to save money buying stuff for my classroom is a new Facebook page that was begun just a couple of weeks ago. Charity Preston from The Organized Classroom Blog started a FB page called Used Teaching Treasures Emporium. There are almost 1,500 members. I have sold a bunch of teaching items that I haven't used recently. I have also bought some new things for my room next year. (It is kinda like what would happen if I worked at Kohl's. I would spend my paycheck on clothes and not really make any money.) The items are in good condition and are much less than if you would buy them new. Just go to Facebook and search for the page. You have to ask to join. It is a win-win situation. You can get rid of some of the books cluttering your shelves and make money to buy new things for your classroom.
If you have any questions about either of these ideas, please email me or comment here and I will try to help you.
Thank you for taking the time to visit,