The AMC huts are located along the AT (Appalachian Trail) in the heart of the White Mountains. This listing below is south to north. For reservations or information call the Pinkham Notch Vistors Center at (603) 466-2727. Here are the rates and details.
Here's a rough map of the huts. A hiker shuttle runs from the AMC facilities and many of the popular trailheads. Here are the details. During the summer season, the huts are open to dayhikers to stop in, get warm, buy some soup, snacks, or gear (hats, gloves, waterbottles) and patches. In general, without a reservation you can't just stop by and expect to stay at a hut.