On this website, you can find more than 500 accredited free online university classes. The layout of this website is similar to that of third party comparators such as kayak.com (for flights) or Zoopla (for housing).
Start by selecting degree (eg Bachelor’s), category (eg Liberal Arts & Humanities), and subject (eg English)
Then, you will be taken to a page that lists online courses offered by various universities:
While most courses will still require registration, all are free and don’t have any pre-requisites. This is a great option for self-learning or supplementary material for a specific course.