If you have college textbooks that the store you bought them from won't take them back, because they aren't going to use them anymore, check online. They were no longer using my husband's math book, so I went online and found a place that would pay me $14 for the book.
One of the worst "visible" expenses I had to deal with at college was books and supplies. If you're a freshman, you will be knocked directly on your butt at the cost of a semester's worth of "educational materials."
If you're looking for second-hand textbooks, check out second-hand book stores and library book sales (I've found brand new textbooks for as little as fifty cents at these sales). You can ask former students and teachers if they're getting rid of their old books.
I am currently attending college and found that the teachers will usually give reading assignments from just a few chapters of the expensive textbooks; however, they are usually known ahead of time when the teacher hands out the syllabus. With that knowledge, you can purchase single chapters of textbooks from ichapters.com - starting at $3.99 per chapter.
Tips and ideas for saving money on textbooks. Consider not buying the book until you've been to the first session of the class. Sometimes you find out that the professor plans to use the book very little, or not at all.
I graduated from college not that many years ago, and picked up a few tips during my years at my university! One of the things I wished I had started doing right away was borrowing textbooks from the campus library . . .