Udacity is geared towards those seeking out nanodegrees, however, they have numerous free courses which the link is directed to. The courses are generally in the engineering and technology arenas. 

Open Yale Courses gives access to a selection of introductory courses taught at Yale. All recordings are available in video, audio, and text transcript formats.

OpenLearning offers free courses but also uses a social media workflow, built-in galleries, wikis, and blog pages to encourage collaborative learning.

OpenCulture has 1,250 free online courses from some of the world's most prestigious universities, such as Stanford, MIT, and Oxford. The courses are downloadable as well.

Open2Study

There's a section for free courses as well as accredited courses that cost a fee. The entire website, including the free section, covers a wide range of subjects.

OEDb has over 10,000 free online courses from sources such as Udemy to Harvard on a wide variety of subjects. We recommend browsing by subject to help narrow down your search.

Microsoft Virtual Academy (MVA) training courses are delivered by experts. Some learning paths help you earn MVA badges.

Merlot has over 5,000 courses that are all free. We recommend using the search area of the website to narrow down the topic of interest and exploring from there.

If you have an interest in learning about social media marketing, Hootsuite Academy has several free courses to explore.