Last August, Kathy Ryan and her 17-year-old daughter, Molly, spent a week in New York City. They shopped in boutiques around Manhattan. They toured art museums and visited colleges. At night, they kicked back in a lavish apartment on the Upper West Side, just a few blocks from Central Park.

All the while, strangers were making themselves comfortable in Ryan’s own home, some 400 miles away in Camden, Maine. They were cooking in her kitchen, sleeping in her beds and lounging on her sofas. And that was just fine by her.

“It was fabulous,” she said.

Ryan is among the many thousands of people exchanging their homes for a week, a month or even longer for out-of-the-ordinary vacations. House swappers say it is not only a great way to find free lodging and explore new areas, it is also a much more comfortable way to travel.

“A lot of people are tired of the stereotypical hotel vacation,” said Ann Pottinger,

owner of Vacation Homes Unlimited of Santa Clarita, Calif. The company’s Web site, www.exchangehomes.com, has 3,000 listings of homes available for swapping in the United States, Canada and nearly 40 other countries. Members can set up trades for a two-bedroom apartment in Tuscany, a seaside bungalow in New Zealand or a mountainside cabin in Colorado.

According to Pottinger, the practice has been around for decades but has grown more popular in the past five or six years because of the Internet. It began in Europe in the 1950s, when teachers exchanged residences with other teachers during summer break.

Pottinger said there is no way to gauge how many people are swapping their homes annually, but one of her customers had two exchanges last year, three this year and has two more planned for 2005.

“It has blossomed,” she said.

Most home-swapping Web sites show pictures of the houses, along with descriptions of the neighborhoods and lists of fun things to do in the area. Most charge membership fees, which range from $30 to $115. Some are geared toward senior citizens. Others are just for singles.

Ryan said she got about 50 requests for swaps in her first year on www.homeexchange.com, another California-based network that boasts 6,000 listings worldwide. In October, 32 Maine homes were listed on the site. Most of the offers Ryan received the first year were from homeowners in Florida, but some were from Belgium, Scotland and the Netherlands. Homes in Maine, she said, seem to be in high demand.

For her, the trade for a New York City apartment was ideal. Besides saving her some money, it also gave her and Molly a chance to experience a place vastly different from their home on the coast.

“We went right into the heart of Manhattan,” she said. “It was a gorgeous apartment. We could not have afforded the accommodations we were in, that comfort level.”

And while they were exploring the city, the apartment’s owner was hosting a family get-together at Ryan’s house, which overlooks the harbor in Camden.

Along with the homes, vacationers sometimes also swap automobiles, bicycles, kayaks and other recreational equipment. For Sue Jones, that means toys, books, games and other comforts for her two children, ages 3 and 8. She and her husband exchanged a one-week stay in their Bar Harbor farmhouse for three separate weekends in a 2,000-square-foot apartment in the art community of Chelsea, N.Y. They have also worked out an exchange for a home in Rome.

“There are a lot of advantages of doing a home exchange, other than the money-saving aspects,” she said. “With a young family, it is important to be comfortable.”

Jones, who lives in Bar Harbor and Boston, said trading houses feels more “homey” than staying in a hotel. You can cook your own meals, do your own laundry and live like locals instead of like tourists, she said. Sometimes you even take care of their pets while they take care of yours.

On her company’s Web site, Pottinger offers some advice to potential house swappers. Be flexible. Give as many details as possible about your home. Ask a friend or neighbor to meet the guests when they arrive. Leave the house in the same condition you found it.

Pottinger said there have been few problems with exchanges, and any incidents seem to be minor. She knew of one swapper who opened a window in a New York City brownstone and accidentally knocked out the air conditioner.

“People go to great lengths to rectify” any problems,” she said. Ryan said you do have to be a bit trusting to participate in home exchanges. She prepares her house for guests by clearing out closets and locking away any personal items, such as clothing or important paperwork.

“And when we arrived in Manhattan, they had done the same thing for us,” she said. If you ask the right questions and reach a good agreement, the rewards of exchanging homes can be great, Ryan said.

“It is a bargaining-in-good-faith kind of thing,” she said. “But I think anyone who lives in coastal Maine, you are in a pretty desirable place.”