The Virtual Homeschool Group offers online courses for homeschoolers for free. (Students still need to purchase course textbooks for most courses.)
Homeschooling parents who were teaching in homeschool co-ops joined forces to create Virtual Homeschool Group site. They provide and maintain the platform, relying on donations for funding. Courses are created and taught by volunteers, so courses vary in design and teaching style.
They offer a variety of types of courses. Some are actual group courses where students and teachers connect in virtual classrooms, while "at-your-own-pace" (AYOP) courses are designed for independent study by an individual student with open enrollment at any time. Courses appear to target about fifth grade and up with many for high school level. AYOP courses are available only for Saxon Math and Apologia Science courses as of August 2020.
Looking through their class archive, it appears that they began with a heavy emphasis on science, particularly courses based on Apologia science textbooks. They have expanded so that there are now courses in math, history, language arts, and a number of electives. You can sign up on their list for notification when new courses are made available for enrollment.
Some courses are more sophisticated than others. For example, among the AYOP math courses, the Saxon Algebra 1 course includes recorded lectures, computer-scored problem sets, and computer-scored weekly tests. But that might not be the case with all Saxon Math courses,
These courses might well be equal to others that cost hundreds of dollars, so this is really a wonderful option made possible by technology and the generosity of those creating and providing the courses.