Don't fall for them! Check out this excellent resource:
Mason OER Metafinder
Mason OER Metafinder (MOM)
Unlike OER crawlers that search static content libraries, George Mason's OER Metafinder (MOM) launches a real-time simultaneous search across 21 sources of open educational materials, providing real-time search results that can update dynamically.
To find more OER resources, please click on the Open Resources tab on the left side of this page.
Open Educational Resources (OER) "are teaching, learning, and research resources that reside in the public domain or have been released under an intellectual property license that permits their free use and re-purposing by others. Open educational resources include full courses, course materials, modules, textbooks, streaming videos, tests, software, and any other tools, materials, or techniques used to support access to knowledge."
"Open access" is the practice of providing unrestricted access to online, peer-reviewed, scholarly materials, including journal articles, books and monographs. Here is a brief introduction from one of the leaders in the field, Peter Suber: