I agree - the automata, computability, and complexity course I took at university was both eye-opening and fun. I'd recommend a course in discrete mathematics

I agree - the automata, computability, and complexity course I took at university was both eye-opening and fun. I'd recommend a course in discrete mathematics beforehand. Furthermore, most CS grads I know would benefit from some statistics knowledge. I've even found physics, linear algebra, and biology (specifically genetics) very useful on the job. I see academic subjects the same way many people see programming languages -- they're tools. If all you know is programming, everything starts to look like a programming problem. There are other kinds of problems, too, and even as a professional programmer I often stumble across problems where (basic) knowledge in another field has helped immensely.