I keep thinking of
the Internet Archive as just a place to get out-of-copyright books free. I need to disabuse myself of that notion. It's more than that. The Internet Archive has
millions of free books written since 1923.
Case in point: Internet Archive's Open Source Textbook Collection. There are currently 2,176 open source textbooks available at the Internet Archive,
here.
A then college student named Andrew Lekashman, with some friends, devoted an entire summer calling professors and researching free textbooks worldwide. This collection is the result of that work.
Hopefully, sympathic professors will learn of this resource and choose to require students to obtain one or more open source textbooks, rather than buy the commercially-published ones. In case you haven't noticed, commercially-published college textbooks can be outrageously expensive. For example, some studies have shown that textbooks may now account for 15% of attending a community college.
Another use that I can see for these free textbooks is for the individual, especially one on a tight budget, using these for self-study of a subject. I personally have preferred classroom instruction for some reason (I've got to admit that part of the reason may be a lack of enough self-discipline to do it on my own), but one or more of these textbooks may be of great help to the highly-motivated student who can teach himself or herself.