SAN JOSE, Calif. — Is it too late for a newcomer to crash the online social networking party?

The biggest gathering by far is at MySpace, which continues to bloat like an online "Summer of Love." The college kids connect at Facebook. The post-college twentysomethings look for dates on Friendster or Xanga, to name just two. The self-expressive types emote at LiveJournal. The career-minded schmooze, if invited, at LinkedIn.

The challenge for new social networking sites, which all promise to give users a community of sorts, is how can they attract users if a crowd isn't already there?

That question hasn't stopped countless new social networking sites from launching, and more that are hoping to launch this year, gambling that consumers are fickle and experimental enough to try something new. Like a new bar or cafe in the real world, if a few people like it, they'll start dragging their friends to the new place.

That's the dream of Cyworld, South Korea's hit social networking site, which entered the American market yesterday with the official launch of its U.S. social networking site (www.cyworld.com). With cute graphics, animated selves to dress and "minirooms" to fuss over, Cyworld hopes to appeal to the 17- to 24-year-old set (with probably about 70 percent of them female) as a place where you can "be yourself," said Henry Chon, the chief executive of Cyworld USA.

"Our whole site is leveraging your offline relationships," said Chon.

Started seven years ago, Cyworld, which is owned by SK Communications, has saturated the desirable young market with 90 percent of people in their 20s signed up with Cyworld accounts.

At Cyworld, users create busy, personalized pages with digital animated models who interact in spaces known as "minihome" and "minirooms." The sites are rich with features, such as a place to show off photos, videos, comments and silly drawings in sketchbooks. In South Korea, half of the company's revenue comes from selling "acorns," Cyworld's version of money. People use acorns to buy specialized "skin," the backdrop to a home page, furniture for their virtual rooms and other features. For example, to buy a flying baby devil for one's room costs 10 acorns (each acorn is 10 cents). The other half of Cyworld's revenue comes from ads.

Acorns can also be used to purchase music tracks, which play when a visitor comes to the site. In South Korea, Cyworld has sold 130 million songs, with the customer paying about 50 cents per song. This feature is not yet available in the United States because Cyworld is still negotiating with U.S. record labels.

In South Korea, 2 million of the 18 million users check and update their Cyworld pages from their cell phones or other portable devices. Cyworld hopes to offer this option in the United States, too.

At its U.S. headquarters in San Francisco, Cyworld had to make changes to itself to work in the United States, said Chon. The characters — called "minime" — became bigger and a little older than the ones in Cyworld Korea.

One draw is that Cyworld is easier to use and more graphically pleasing than most MySpace accounts. But MySpace has been successful despite being clunky, industry analysts point out. "MySpace is huge. And it's still hard to use," said David Card, a senior analyst with JupiterResearch.

Another draw is that people will see Cyworld as more intimate, more slumber party than stadium concert scene. U.S. focus groups of young people have apparently reported back to Cyworld that even with all the different kinds of online social networks out there, young people feel something's missing.

Cool "is a hard mantle to wear 24/7," said Michael Streefland, Cyworld's vice president of marketing. "Cyworld is about your real world, your real life."

Already, 15,000 people have signed up for Cyworld accounts to help the company test out its site.

One of them is Elizabeth Johnson, 21, a senior at the University of Oklahoma. An English major, she has accounts with MySpace, LiveJournal, Xanga and Facebook, in part to reach different groups of people.

Her roommate, a computer novice, loves Cyworld, Johnson said. Cyworld "has a little bit more wholesome attitude" than other sites.

"MySpace isn't really cool unless you know coding to make it look pretty," said Johnson. With Cyworld, "It hardly takes any effort to decorate your room."