Why not print your own textbook! The Public Library of Cincinnati has a book printing machine that can produce an inexpensive book in just a few minutes.
Affordable Learning Georgia Tutorial: Creating and Modifying Open Educational Resources - this is an excellent tutorial on how to create your own OER and adapt others' OER to your course.
Everything published by the Federal government is free of any copyright restrictions. The research, reports and websites can be useful resources for classes when creating your own course material.
The Homeland Security Digital Library is a collection of documents related to homeland security policy, strategy, and organizational management. Topics include maritime, unmanned aerial systems, terrorism, epidemics and many more.
SciTech Connect is a collection of science, technology, and engineering research information from the U.S. Department of Energy.