I'm an STS student, so bear with me; I'm happy to provide clarification but I want to leave the specific application unspecified:
What sources would you consult if you were trying to generate a huge "list of all academic topics"?
I'm thinking it would include all the 'ologies', the 'isms', the 'X studies', all the historical "movements", all the 'subjects' of journals and papers, all the 'big questions' of any given "field".
What other sources, whether vague (like above) or specific (like a URL with some good list items), would you suggest in compiling this list?