Hi, edX is a website where you can take courses from some great universities. While some of the courses are absolutely free, some others cost a little money(around 50$). I completed my first free course earlier this month and it was a really good experience overall. The exams and assignments were pretty challenging so I learned a lot about the basics of Python and object-oriented programming.
As most courses are more on the introductory side, these free courses might be interesting for some TAO people who are just starting out or trying to further establish their fundamental skills:
Linear Algebra - Foundations to Frontiers(University of Texas at Austin)
Introduction to Computer Science(Harvard)
Effective Thinking Through Mathematics(University of Texas at Austin)
See you in the lectures if you register!