Currently not much reporting is available on Categories. it will be useful to have a report that list all the courses (and other learning items) and the categories that they are associated with listed.
For tags, i use the courses.csv report from the data dump, which does not have a column for all the associated tags but the information is appended with the course name. Not the best way to get the data but works. If something similar can be made available for categories it will serve as a work around while a robust categories reporting is developed