In college, I tried to take one "fun" course a semester. I might have been somewhat constrained by gen ed and major requirements, but I still tried to choose something that sounded "fun" - especially when it was to fulfill a (semi-)pointless gen ed requirement. Off the top of my head, I took an Art for Non-Art Majors class (drawing), Zen, a two-semester series on Fantasy and Science Fiction Literature.
As the kids are getting older, I am thinking about taking one or two classes a semester at the local community college.