Calling all firefighters, ninja fans and contortionists. And hipster moms, diabetics, dog lovers, would-be models and ultralight aircraft pilots.
No matter who you are, somewhere in cyberspace a social network exists - or soon will - to cater to your interests.
While mega-sites such as Facebook and MySpace compete as generic, all-purpose platforms for online schmoozing, a subculture of boutique gathering places is emerging.
Columbia resident Dave J. Iannone runs one of them. In July, he started FirefighterNation.com, a networking site for U.S. firefighters and emergency medical services and rescue workers.
The site has attracted 10,000 members from around the country - and collectively they've posted nearly 32,000 photos with their profiles, including family pictures and images of blazes they've battled.
"You have a user base that's very engaged," said Iannone, a member of the Hyattsville Volunteer Fire Department since the age of 12 whose day job is interactive media director for a magazine publisher.
"They are able to connect and talk and have personal discussions that they can't have anywhere else," Iannone said. "People have ultra-specific interests, down to what kind of firetruck they like to drive."
This is typical of the genre, according to Barry Wellman, a University of Toronto sociologist who studies these online gatherings.
"There are two ways to do it," he said. "You can have a general network or a specialty network. I think these specialty networks are where things are going in the future."
Using the Internet to connect people with common interests is hardly a revolutionary concept. E-mail listservs, Usenet newsgroups and electronic bulletin boards were attracting devotees of various causes and hobbies long before the World Wide Web took shape in the 1990s.
But the cutting-edge social network programs developed in recent years are far more versatile. They allow users to create Web-based personal profiles which they use to communicate through multiple channels - sharing pictures, videos, messages and blog posts - not to mention "friending" one another.
(Friending is the official process of asking a social networking subscriber if you can be his or her friend - and vice versa. This generally grants the new friend access to the subscriber's profile and personal posts.)
The success of these efforts has been phenomenal by any standard. Facebook alone - which broke from its early niche as a network for college students last fall and opened its rolls to anyone with an e-mail address - now boasts 53 million members.
Meanwhile, outside the glare of attention focused on Facebook and MySpace, a community of narrowly focused, "vertical social networks" began to proliferate.
As a result, today's dog lovers can create profiles for their pooches on Dogster.com, while felinists can put their cats on display at Catster.com.
Fans of AskANinja.com, a popular Web site with videos that star a hooded man dressed in black, can debate the merits of recent episodes with more than 5,000 other ninja-istas on the site's companion network.
The flexible of limb connect on Contortionists Unite!, trading tips on stretching and sharing photos of themselves pretzeled into a variety of improbable positions.
Iannone runs his site using a software platform developed by Ning, a San Francisco-based company that allows people to create their own social networks free of charge. Co-founded in 2004 by Marc Andreessen, creator of the Netscape Web browser, Ning now hosts more than 100,000 networks.
Many are hobbyist sites, such as TrikePilot.com, a network of several hundred people interested in flying ultralight aircraft (many of which have three wheels, hence the name). Others focus on topics that include schools, bands, religion, movies and sports.
Not all 100,000 social networks are created equal. Many have just a few members, and the top 200 sites get 40 percent of the traffic. Ning earns revenue by running Google advertising links on its members' networks or by charging network founders for running their own advertising and other premium services.
Manny Hernandez of Orlando, Fla., started a network for diabetics called TuDiabetes.com that now has more than 1,600 members worldwide.
"It gives them the ability to connect with others and not feel alone anymore," he said. "In general, what people find is a very friendly and welcoming environment."
Hernandez was diagnosed with Type 2 diabetes in 2002 and decided to start his site after reading The World is Flat, a best-selling book on globalization by New York Times columnist Thomas L. Friedman.
"It's an international site," Hernandez said of his diabetes network. "There's a really interesting exchange when it comes down to how they manage their disease in different countries."
Like other specialty networks, TuDiabetes attracts people who are passionate about the subject - and their interactions sometimes reflect the strong feelings.