They are available for free downloads from their publisher with an appropriate name: Freeload Press. There are quite a few text books in the humanities and social sciences, along with self-help titles on programming languages, etc. Check out their Book List.
I learned about this from Brad DeLong's post on the new Principles of Economics by Timothy Taylor, described by DeLong as "The Best Intro Econ Teacher I Know."
There is also this increasingly popular free opencourseware by MIT that many may be aware.
ReplyDeletehttp://ocw.mit.edu/OcwWeb/web/home/home/index.htm