Aficionados of antique and secondhand furniture stores love Portland. Good browsing may be had on Congress Street. Check out the stretches between State and High streets in the arts district and from India Street to Washington Avenue on Munjoy Hill. About a dozen shops of varying quality are in these two areas.
More serious antique hounds may choose to visit an auction or two. Two or three times per week you'll be able to find an auction within an hour's drive of Portland. A good source of information is the Maine Sunday Telegram. Look in the classifieds for listings of auctions scheduled for the following week.
For new items, the Old Port, with dozens of boutiques and storefronts, is well worth browsing. Though it has a few chain stores and lacks a quality bookshop, the commercial neighborhood is strong in contemporary one-of-a-kind clothing that's a world apart from the stuff you find at malls. Artisan and crafts shops are also well represented.