There are many sources of open lectures and tutorials:
Free online lectures from universities such as Berkeley, UCLA, Harvard, MIT, Princeton, Stanford, Yale and others. Subjects covered include: Astronomy, Biology, Chemistry, Computer Science, Economics, Engineering, English, Entrepreneurship, History, Law, Mathematics, Medicine, Philosophy, Physics, Political Science, Psychology, and Religion.
An online collection of thousands of video tutorials on subjects such as mathematics, history, finance, physics, chemistry, biology, astronomy, and economics.
Open Yale provides lectures & other materials from selected Yale College courses free of charge via the Internet. The courses span the full range of liberal arts disciplines: humanities, social sciences, & physical & biological sciences.
There are many potential sources of open textbooks which learners may find useful. A few significant sources are:
The Open Textbook Library is a curated, browsable collection of over 200 open textbooks housed at The University of Minnesota and sponsored by the Open Textbook Network.
The Multimedia Educational Resource for Online Teaching (MERLOT), developed by the California State University Center for Distributed Learning offers access to thousands of open educational materials. The search function even allows you to enter an ISBN number of a current textbook to find a comparable open textbook.
OpenStax College at Rice University
"OpenStax College is a nonprofit organization committed to improving student access to quality learning materials. Our free textbooks are developed and peer-reviewed by educators to ensure they are readable, accurate, and meet the scope and sequence requirements of your course."
Note: Required texts for a course are selected by instructors.