For fun:
Everything from attending a play at Court Theatre to hanging out at Jimmy's Woodlawn Tap, Bar Louie, or the lakefront.

If you have two hours in Hyde Park:
Visit the Seminary Co-op Bookstore and grab a bite at Valois.

If you have two days in Hyde Park:
Visit the Oriental Institute Museum and the Museum of Science and Industry. Spend some time at the lake or go skating on the Midway. Get some pizza from Giordano's or Medici.