Depending on your interests, you can make a nice day of it in Hyde Park. Hyde Park is home to the University of Chicago. In addition to touring the university grounds, my suggestions would include:

The Robie House--generally acknowledged as one of Frank Lloyd Wright's most important works and a perfect example of his prarie houses

The Oriental Institute--a great collection of antiquities from the middle east

57th Street Books & The Seminary co-op--these are two sister bookstores. The former is a very good general interest bookstore, with a particularly strong section on Chicago history, architecture etc. The Seminary co-op is more focused on academic titles and is considered to be one of the best bookstores in the world for university press titles.