America:For millions of Americans it's the favourite place to rent an apartment, find a job, sell a car, buy a sofa, get a date or arrange a brief encounter.
But the success that has made Craigslist an essential part of modern life in the United States is alarming newspapers in the country's big cities, some of which fear that the internet bulletin board could drive them out of business.
Founded in 1995 by Craig Newmark, a San Francisco computer programmer, Craigslist (www.craigslist.org) now operates in 90 cities in 35 countries, with more than 10 million users and three billion page views every month.
Mr Newmark thinks of the site as a community rather than simply a business, it carries no lucrative banner ads and offers almost all its services free.
Until now the only fees charged have been for job ads in New York, Los Angeles and San Francisco - bringing in an annual revenue of more than $20 million. Craigslist will soon charge estate agents in New York $10 to advertise apartments in the city, half a million of which appear on the site every month.
You can buy everything from a dog kennel to a suburban house on Craigslist, join a club, sound off on politics or religion and find a mate or simply relieve your boredom.
"I don't go out very much because I do not drink. I quit smoking when I moved here and that was the best decision I have ever made.
"I jog and hike in my spare time. I was hoping to go skiing too when it gets a little cooler. Weird winter we are having so far," a 27-year-old woman in Virginia said on the Washington DC site yesterday.
"I would love to meet a friendly man who might share the same interests as I and might want to have a date at the zoo. I am 5'5", 120lbs long blonde hair and green eyes. I like tall men. The only thing I ask is you do not have a drinking or drug problem, you have a job. Thanks!!"
Mr Newmark said this week that although there are occasional problems with tricksters and scammers, he receives few complaints from users about personal encounters or business transactions arranged through Craigslist.
"People expect other people on the site to be trustworthy," he said. "We're all aware that there are the occasional bad guys, but somehow this whole thing works and works pretty well."
Internet giants like Google, Yahoo and Microsoft have watched Craigslist's rise with envy, launching their own, glossier classified ad services.
Mr Newmark is relaxed about rival sites, predicting that the big corporations will be unable to simulate Craigslist's sense of community.
"We don't view other sites doing similar things as competition. We figure there are a lot of human needs out there that need to be addressed," he said.
"We run as a community service, kind of a public trust, and as long as corporations are genuinely helping people that's a pretty good thing."
If internet firms are envious, newspapers are horrified as they watch classified ad revenue shrinking in America's cities.
A business study in the San Francisco Bay area, Craigslist's biggest market, has suggested that local newspapers are losing $50 million a year in advertising revenue.
Craiglist's attraction for advertisers is not only that it is free but that ads can be longer than most newspaper classifieds and can include pictures. Job ads on Craigslist attract younger applicants than newspaper ads, and the charge of $75 in San Francisco, New York and Los Angeles is a lot lower than for a conventional ad.
Although Craigslist has opened sites for a number of cities outside the US, including Dublin, it has not yet established a foothold in foreign markets.
Newspapers outside the US may not escape the Craigslist effect for long, however, as Kijiji, a rival site run by eBay, has started to take off in continental Europe.
