On a recent Monday in June in Austin, the local Craigslist "women seeking women" page lists 41 posts. Six of them concern the relative merits of plain or puffed Cheetos. Nine hash out the consequences of a bar's recent closing. Three women discuss whether it would be fun to sleep with Food Network star Rachael Ray.

Yet going over to the "men for men" section is like walking into an after-hours bareback sex party. By clicking on a disclaimer, you swear that you are over 18 and not bothered by explicit content and that you release Craigslist from any liability that "may arise from my use of the site." The first headline begs for a special kind of oral asphyxiation "until I pass out." About six lines down, after "desperate for some" and "hot mouth," comes the query "Any kinky young guys in Austin?"

Hello, kinkman! You are on Craigslist.org, along with plenty of kinky young guys and your junk-food-eating lesbian sisters. You are joined by desperate housewives looking for men, families seeking pets, students who need roommates, and executives without jobs. You are one of 5 million people to post an ad this month in any of Craigslist's approximately 170 cities and regions in 34 countries (with another two dozen or so planned in about 10 nations), and you are writing in a category that belongs, almost exclusively, to men looking for instant sex.

Yes, there are kinky young guys in Austin. In fact, there is everything on Craigslist, the low-tech Internet site that is outdrawing, outperforming, and outshining its high-tech counterparts. It is fast. It is free. It is uncensored. It is anonymous. No wonder it's growing by leaps and bounds, and no wonder it is particularly embraced by gays and their prospects.

Founded in 1995 as a general resource for San Francisco by Craig Newmark, Craigslist began to branch out in 2000 and evolved into a world of cyber communities that is now expanding organically like something out of an early Star Trek episode. From 32 cities at the end of 2003, Craigslist locations jumped to 75 by the end of 2004; that number has more than doubled in the first six months of 2005. It takes time for a city to build momentum and for a Craigslist community to take off. But once it does, look out.

In early 2001, Austin was among the first 15 Craigslist cities, but only recently has the site become the talk of the town. Its now-thriving communities of "men seeking men" and "women seeking women" are nonetheless hard to compare with those of San Francisco and New York, the top two locations in overall traffic.

The number of men seeking men in the San Francisco Bay area on any given day is in the hundreds, sometimes thousands. According to Jeffrey Klausner, MD, MPH, director of sexually transmitted disease prevention and control services for the San Francisco Department of Public Health, Craigslist is the second most frequently mentioned Internet source in San Francisco for men who have contracted syphilis. The site, he says, is a place where a man "can get a new sexual partner in minutes and with a little extra effort can hook himself with crystal meth or other drugs."

Klausner has met several times with Newmark and Craigslist CEO Jim Buckmaster urging the executives to take a more active stand to promote sexual health. For the moment, however, Craigslist adheres to the company mantra of letting customers police themselves.

The San Francisco site has let the City Clinic add a link to the "men seeking men" disclaimer page, plus a link to a safer-sex forum that is supposed to be monitored by City Clinic staff. The forum appears to be filled mostly with worried men reporting spots, bumps, and rashes and receiving advice from other men who may or may not be experts but sound like they know what they're talking about.

As for policing the site for barebacking or other risky behaviors, Buckmaster says Craigslist does not want to be patronizing. "We have a very small staff here," he says (Craigslist employs 18 people). "We tend to focus more on trying to minimize illegal activity, which is more in the area of drugs."

At the same time, Craigslist always reacts to feedback. "We're open to trying to make any changes at the site that people think would be effective," Buckmaster says, adding that the men who frequent the various "men seeking men" areas seem happy with the way things are. Far more complaints arise from the "women seeking women" rooms, where lesbians argue about issues like "Should bisexual women be allowed to post in the women's area?"

Craigslist retains the ability to bar users based on their e-mail addresses, though Buckmaster notes that the transient nature of Internet provider addresses makes enforcement difficult. Users can "flag" an inappropriate poster, whose post will be deleted if enough flags accumulate. The site has also made it difficult to flag a comment more than once, in order to prevent someone from knocking a poster off the system out of personal pique.

Self-policing aside, the advertising-free cyber space has the easygoing feel of a friendly neighborhood bar, the kind with a couple of back rooms and a few dealers hanging around outside.

When London's site got under way, the "casual encounters" area, an enclave of mostly straight pleasure seekers, had an unusually high ratio of women to men, roughly 50-50, as opposed to the typical 10 males per female. But just a day after an article in London's The Observer newspaper described the phenomenon, that ratio jumped to 100 men per woman, staying that way for weeks.

"The site was described as a place where the girl next door is looking to hook up with you on a casual basis," Buckmaster says. "Well, I don't know what else you could possibly write in an article that's going to draw more eager males. It was like throwing a chunk of raw meat into a shark tank."

The London example illustrates a fact of life that can be captured only by an all-embracing forum that transcends sexual orientation: Men and women have profoundly different attitudes toward sex, and in this domain, gay men probably have more in common with straight men than with gay women.

These discrepancies tend to conform to the stereotypes we've all heard about gay men and lesbians: Lesbians might not put out for you on the first date but will marry you on the second. As for gay men: A trip through almost any Craigslist city site suggests marriage takes a backseat to an endless series of, um, wedding nights.

Back in the Austin women's section a 30-something asks, "What makes you happy?" Ten women promptly answer with a litany that includes shopping, pedicures, music, and "watching a bird fly by." Over in the men's area, meanwhile, the language is less Martha Stewart and more Chi Chi LaRue.

It's not all flowers and dirty minds, however. Over in the site's "queer" discussion line, an area that unites like-minded users from all the Craigslist cities, the two sides of the GLBT populace are reunited. A man asks what he can get a 63-year-old single lesbian for her birthday. Among the suggestions: a power drill, a gardening kit, a dildo, and "another 60-ish single lesbian." In Atlanta a man seeks a gay roommate. In Shanghai a gay American tourist looks for a travel companion in a country where the guys, he says, "are living in the Stone Age days." In Boston a user hopes to assemble a men's discussion group. In northeast Denver someone plans a community picnic.

Craigslist's founder has resisted millions of dollars in advertising and investment offers. "Sometimes I've winced when I thought about how much money I've walked away from," Craig Newmark told the Associated Press in May. In exchange, however, he has taken a marketplace of jobs, love, homes, sex, and ideas and eventually made it breathe on its own and exhale the essence of a city.