Lawrence University is one of the best small liberal arts colleges in the Midwest, and its Conservatory of Music gives Appleton a cultural life well beyond what you'd expect from a city this size. The campus sits on the south bank of the Fox River, and its pleasant mixture of Victorian and mid-century buildings is worth a wander.
The university mounts regular public events — concerts, lectures, theater productions — most of them free or cheap. The conservatory presents student and faculty recitals throughout the academic year, and the summer brings chamber music and jazz performances. If you are in town during the school year, check what is on before you assume there is nothing to do in the evenings.