The best place to find mathematics, mathematical literacy, physical science, and even some accounting, geography, life science, even some CAT and IT resources. this is vetted by the Department of Basic Education in South Africa, and is filled with helpful explanations, examples, and practice activities. 

This provider of textbooks and eCourses has an awesome variety of free texts and resources. If you just don't get how your textbook explains things, you may be able to get a full text (or a sample of a full text with helpful notes in it) or summaries at this website. 

FoondaMate is your AI study buddy, right on WhatsApp or Messenger. It contains a wealth of resources including past papers, instant answers to questions in a variety of subjects, and detailed solutions.

This resource isn't exactly free, but at a low cost of R5 a day or R30 for a whole month, it really is worth it. 

This is a collection of free apps that are chockfull of practice activities and past papers in a variety of subjects. Many students like using this app as it is free, allows them to practice past papers on their mobile devices, and uses minimal data. Check out the Android apps here, the Hauwei apps here and the Apple apps here.

For extremely helpful maths worksheets for grades 8-12, try Sharp Mathematics. There are also a few notes and additional resource to supplement the worksheets. What's really great about these worksheets is that they start off with the basics, then progressively increase in difficulty with the last few questions often emulating exam-type questions.