Hostels. To many, they conjure up connotations of cheap, loud, and young. But over the years, I've come to suspect that the people who get the most out of hostels are often adults traveling as couples, families, or groups.
At many hostels, dorms are not the only option. Plenty offer private rooms for two to six people. It's usually pretty easy to discern the accommodations options online through sites such as Hostelworld.com, Hostels.com, or Hostelling International (HI). Sometimes private rooms even have their own bathrooms, which puts them a step above many pensions and small inns.
The absolute best way to witness the joys of hostelling for this demographic? Visit the kitchen or dining room. It's here you'll often find enthusiastic adults just returned from the local markets cooking up a storm.
I remember staying in the Youth Hostel La Fontasse, situated on a bluff outside Cassis in the south of France, and walking into a boisterous kitchen full of adult Germans, Swedes, and French all sharing counter space and recipes. Each evening at the Fontaine de Vaucluse Hostel in Provence, the long picnic tables in the courtyard were heaped high with intricately prepared dishes featuring local ingredients, while at the Chalet Martin in Gryon, Switzerland, people prepared hearty portions to fortify themselves for alpine hiking, then dined at tables overlooking snow-capped mountains and a steep green valley.
If you're an adult considering hostelling, but want to avoid the college dorm feeling, consider staying at a hostel in a smaller town or rural locale. Because of rental-car age restrictions, you'll often find that adults outnumber youths staying at hostels primarily accessible by car.