Some of the most popular subject areas are: Computer Service, Language, Data Science, Business and Management, Engineering, and Humanities. There are tons more to choose from. Online courses can be taken for free. These could be used for professional development opportunities. I especially liked "The Foundations of Happiness at Work". : )

This is a resource that would be excellent for a health science, social studies, history, or sociology class. It could also be helpful for a debate club or something similar. It provides resources (handouts, videos, graphs) to be used by students and teachers to examine universal healthcare around the world. PBS also offers lots of other topics that could be used at all different age levels.