See the list of all the courses offered at the National Open University of Nigeria (NOUN). The list of NOUN university programs is arranged according to faculties in the school and you can also crosscheck with info on the NOUN website.
But before that, it is important you confirm (from NOUN) the status of any of the courses listed before applying. There could be discrepancies, including in things like the department has been accredited by the Nigerian Universities Commission (NUC) or not.
Since this list might change at any time, I have decided to provide you a direct link to the NOUN webpage that lists all their available courses. Please see them at nouedu.net/programmes