Check out the Gothic Cathedral, and the antique center nearby. There is a wonderful antiques and brocante market along the Quai every Sunday. On weekday mornings, go to the Marché du Capucins for excellent produce, seafood, cheeses and even sushi!
The longest pedestrian shopping street in France, Rue St Catherine is an excellent place to restock your wardrobe. You'll find many things that are stylish and reasonably priced, as well as name brands.