Futurelearn are providing a wide range of free short courses offered by different universities on subjects from Teaching to Sustainability. We recommend some of our own learners study these in tandem with our courses.
I’ve joined a few of these myself and find them excellent. You usually need a few hours per week to complete the course activities which are suitable for all levels of student. At the end of the courses you can apply for a certificate of participation although there is a fee for this. The course itself though is free along with any necessary software/resources used. I thoroughly recommend these as an introduction to topics you may with to study further.