At first, Yahoo! 360 will be accessible only to those invited to participate by the Sunnyvale, Calif.-based company, which in turn will be able to invite others to the service. Yahoo! employees have been experimenting with the service--known internally as "Mingle"--since last year, a Yahoo! spokeswoman confirmed.

"This is the response to customers' desire for an easy and secure way to further connect with their friends and family over the Web," Paul Brody, senior product director of community products at Yahoo!, said. "Users have the choice to show as much or as little of their personalized content and information to as many or as few people as they like."

Eventually, Yahoo 360! users will be able to link to photo albums, blogs, and other content stored on non-Yahoo sites, said a spokeswoman. Brody declined to say whether the feature will be ad-supported.

With its new offering, Yahoo! will be joining a crowded field on both the blogging and social networking fronts with its new service: Google already has Blogger; Microsoft's MSN.com has MSN Spaces; and Ask Jeeves has Bloglines. On the networking side, Yahoo! will face challenges from innovative social networking providers--MySpace, Friendster, Google's Orkut, and Lycos Circles.

MySpace.com, the leading social networking site, drew 8.9 million unique visitors who generated 4.6 billion page views last month, according to comScore. But Yahoo!'s tremendous user base might help it quickly catch up. Last month, Yahoo! drew 110 million unique visitors, who were responsible for 30 billion page views, according to comScore's Media Metrix.