Our World in Data is a really interesting, and never-ending, website where you can find legitimate data on just about anything imaginable - not necessarily science data, like for physics, but governmental, societal, global, health, and so many other areas and fields that are out there! All the sources of information are vetted and provided on everything this group does. This could be really useful for those who are doing historical and social science type research.
For those looking for science data, a good starting point is on the CABS site: online datasets.