At last count, no fewer than 21 major cities have created "greeters programs" operated by persons who volunteer to lead visitors around the town they love. These are officially sponsored civic programs in which the tour guide receives nothing for his or her services (and would be offended if offered payment), although the visitor is supposed to pick up any costs of transportation or snacks consumed en route. The number of such cities has rapidly grown in the last two years and they presently amount to 21. In addition to the U.S. cities of New York, Chicago, Houston, and San Francisco, they include Toronto, Melbourne and Adelaide in Australia, Paris, Moscow, Belgrade, The Hague, Buenos Aires, Brussels, Marseilles, Brighton and Kent in England, and several others. For further details, see www.globalgreeternetwork.info.

But travelers should know that several other, somewhat similar programs are offered by individual entrepreneurs in a slowly growing group of other cities. These, quite frankly, have only recently come to my attention, and it should be stressed that people taking such tours are expected to pay something for their tour -- an amount which they, the visitors, determine, and which usually should be about $10. In effect, you accept a free-of-charge tour, but tip the tour guide at the conclusion of the tour.

Examples? D.C. by Foot (www.dcbyfoot.com) runs what it characterizes as "free, tip-based walking tours," two hours in length, of the nation's capital, on which participants are expected to slip about $10 to the guide. Tour Guys (www.tourguys.ca) operate free-of-charge walking tours in both Toronto, Ontario, and Vancouver, British Columbia -- they rely on tips for their remuneration and charge no fee for their basic tour in each city. And finally, RunnerBeanTours of Barcelona (www.runnerbeantours.com) does the same, and provides an excellent tour by highly-motivated young graduate students of local universities; currenly they offer a "Free Gaudí Walking Tour" and a "Free Old City Walking Tour", and they are working on a free "Kids & Family Walking Tour" to be offered at some time in the future.

I'll be naming other tip-based walking tours as they come to my attention, and would appreciate receiving the names of companies that may be known to readers. Everyone with whom I've spoken about the Washington, D.C., Toronto, Vancouver, and Barcelona free walking tours has been absolutely enthusiastic about the experience they had.

Photo Caption: Brussels' rue du Marche aux Charbons. Janet M. Powers/Frommers.com Community.