Cram Tokyo, Seoul, New York City, Mexico City, and Mumbai together into a single megalopolis, and its population would still be smaller than that of MySpace, the online social-networking juggernaut. And for a newbie, joining MySpace can feel much like being lost in a city with 120 million inhabitants. There are thousands of people around you who share your interests and could become your friends--but how to connect with them?

For Internet users who want to network with like-minded people without being subsumed into the madding crowd, there is now an alternative. Last week Ning, a Palo Alto, CA, startup cofounded in 2004 by online marketing executive Gina Bianchini and Netscape founder Marc Andreesen, launched a free Web application for creating and customizing boutique social networks--in effect, mini-MySpaces, or "social niche-works," as some are calling this new genre.

For example, I used Ning to create a social network especially for devotees of digital macrophotography. People who join my network have the ability to create their own personal profiles, upload photos, connect with friends, send instant messages, write their own blogs, contribute to forums, and the like. I created my Ning network in minutes using a simple Web interface reminiscent of the blog-building tools from sites such as Blogger, LiveJournal, TypePad, and WordPress. (Now, of course, I just have to recruit a few members.)

In fact, Ning makes setting up a custom social network as easy as starting a personal blog, possibly laying the groundwork for a new generation of Web destinations catering to the planet's endless variety of subcultures. During the yearlong beta-testing phase preceding last week's official launch, Ning users created more than 30,000 social networks, including groups for microbrew enthusiasts, Pez candy-dispenser collectors, natives of the tiny Caribbean nation of Curacao, and Phillips Andover Academy's class of 1972.

 Mainstream social-networking sites such as MySpace and LiveJournal have long given users the ability to create and join specialized groups. More than 5,000 people belong to the black-and-white photography group on MySpace, for example. But Ning's custom social networks come with communications tools such as live chat rooms that aren't available on LiveJournal and other platforms. And Ning's networks seem to occupy a previously unfilled niche in the social-computing ecosystem: they provide an outlet for expression and communication that's more social than a solo blog yet less cacophonous than the forums afforded by the giant social-networking sites.

"It's a continual evolution," argues Bianchini, Ning's CEO. "The Web pages of the 1990s became the blogs of the 2000s. Now blogs are becoming social networks and communities."

To start a social network on Ning, users must first sign up for a free account. Ning's software then walks them through the design process step by step, allowing them to choose a name and description for the network, pick the features (such as blogs, photos, chat windows, and forums) that will appear on the network's main page, and arrange these features however they'd like. Networkers can go with one of a few dozen themes and color schemes provided by Ning, or, if they'd prefer, substitute their own HTML code and style sheets. "Everything is customizable," says Bianchini.

Members of social networks on Ning can even override the network's design, choosing their own themes or writing their own HTML for their personal pages. Control, in other words, is in the hands of the users. "People are doing really interesting things with their MySpace pages, but fundamentally, MySpace is still a walled garden much like the original AOL or Compuserve or Prodigy," Bianchini says. "There is a narrow and fixed view of what people can do, and you can see people pushing up against the limits."