Definetly take the time to walk among Assisi's medieval houses and shops. Most of the cobblestone streets and alleys will take you to the basilica of St. Francis.
Assisi has about 6 cool churches to visit, and then there's the Basilica of St. Francis. But one of the best things to do is hike up to the top of the hill above Assisi and see the castle overlooking the town and the valley below.
There are several little ice cream shops and pizza shops.