I have not yet finished my master's thesis, so I could still take any CS courses which I like. But I think that I can learn the same things easier by reading books and doing some exercises, without going to the courses (and getting stress from the exercises and exams). Another option would be to just listen to the lectures, but without officially taking part in the course (at least here in the University of Helsinki the lectures are public for anyone to listen).
Here are the things that I would like to learn next: functional programming, distributed systems. Compilers would also be an interesting topic, but I don't need that knowledge right now.
My university would have courses about all of those, but now I prefer learning them by myself. I'll download the course material and exercises from the lambda calculus and the Haskell courses, and read a book or two about distributed systems and algorithms.