If you're looking to engage the intellect, the university museums are a fantastic choice. While small, the exhibits are well curated. The Zuhl Museum, in the visitor center, holds a beautiful collection of polished petrified wood, minerals and fossils, including a nest of dinosaur eggs and a baby mammoth skeleton! The University Museum (1280 E University Ave), in Kent Hall, is also worth a browse, with exhibits on regional culture and history.
The Zuhl Museum is also open from noon to 4pm on the second Saturday of the month.