Historic Westminster Arts District in Denver, Colorado, is part of a successful rejuvenation effort for the south part of the town. Several galleries and other shops and a sculpture garden/park give lend a wonderful backdrop to community events.
The Museum of Fine Art in St. Petersburg, Florida, is small but impressive. I've visited it more or less regularly for years, and they present quality exhibitions in a professional environment. A 2006 expansion allows the museum to offer a cafe and respectable gift shop, in addition to their permanent collection and revolving exhibits. It's a fine way to spend an afternoon, especially if you include the nearby Dali Museum in your itinerary.