Open Educational Resources
In order to reduce the cost burden on students, I have switched to utilizing Open Educational Resources (OERs) and online materials, with the limited exception of inexpensive ($10 or less) mass market paperback books. I also develop new materials over time, especially for classes that I teach regularly. Some of these materials will be published as OERs in the future.
As I encounter repositories of OERs for the computing sciences, I will try to link them for the benefit of other instructors.