Please see the lists below. If you have any, please add in comments section.

1. Studony/Shawacademy: You can get a lot of free diploma courses with Shaw Academy/Studony. Courses includes digital marketing, social media marketing, nutrition, content marketing, photography, finance and many more. You can get started with a free one-month course via http://www.studony.com.

2. IBM Data University: Data Science is becoming popular everyday and data scientist are among the highest paid employees in the world. IBM Data University offers free courses on how to use R and Python to analyse data and generate insights. You can visit https://bigdatauniversity.com/ to get started with IBM Data University.

3. DataCamp: If you'd like to study data science in a very friendly learning environment, I will suggest you try Datacamp. While you can study for free for a limited period, there monthly subscription fee is just around $29/N9000. It's worth an investment as the classes are fun. You can register using this invite link: https://www.datacamp.com/invite/q9GJYSkoLXGiY and get free access (limited number of days).

4. Coursera: With Coursera, you can learn from some of the best universities in the world. They offer most of their courses for a fee but you can always bypass that by applying for a fee waiver. Just fill a form, explaining why you are unable to pay the fee and you will get free access almost immediately. Visit http://www.coursera.org/.

Other links are:

Http://www.edx.org
http://allison.com
http://udemy.com