MIT OCW- free MIT course materials online!

I am reviewing MIT's list of courses they provide for free via their OCW site. I first became aware of this site last year, and used and cited some of the material in my writing classes.
Descriptions of MIT's open courses, and the list of courses, which is very extensive, is listed at the following link: MIT OCW courses

Here is a brief overview of this free service from MIT's site:
"“The idea is simple: to publish all of our course materials online and make them widely available to everyone.”
Dick K.P. Yue, Professor, MIT School of Engineering
Unlocking Knowledge


MIT OpenCourseWare (OCW) is a web-based publication of virtually all MIT course content. OCW is open and available to the world and is a permanent MIT activity.
View a list of our most visited courses
Empowering Minds


Through OCW, educators improve courses and curricula, making their schools more effective; students find additional resources to help them succeed; and independent learners enrich their lives and use the content to tackle some of our world’s most difficult challenges, including sustainable development, climate change, and cancer eradication.
Read more about how our materials are making a difference"