The Open University in the UK offers OpenLearn, giving free access to some of their learning resources. You’ll find materials on a range of subjects. Try as many as you like for free. Some are ‘tasters’ of longer courses for which you need to register and pay, and some are standalone offerings. A variety of multimedia are used – some are written only, while others include audio and/or video material.
Below is just a small selection that caught my eye: