For most of these disciplines, you are likely to find data stored within data repositories. Much of the research that comes out in these fields is funding by the National Science Foundation (NSF), which holds specific data storage parameters before funding certain research projects. See the list of repositories on the home page, but you will often find data stored in either one of those repositories or another data storage site held by either a university or government entity.
For certain majors (ex. Math, Data Science, Computer Science, etc.) data can qualify in a number of different fields. What often makes these fields unique though is their thorough use of statistical analysis software. Below is a list of a few free and open-sourced materials that can be used for these majors:
Here too are some software that require a paid license to use (most of these commonly used for more statistical research purposes):