I enjoyed learning more about painting, colors, composition. It has helped me with UI work, presentations, and 3D Blender.
Creative writing too, great to help with documentation, blogs, and organizing thoughts.
Did a sailing class too, not much related to IT, but interesting. Especially navigation, lat lon, the instruments used, etc.
As for IT related coursea, I think re-taking basic classes like compilers, linguistics 101, data structures, calculus, is always fun to remember and learn as well.