"Get ready for total inundation"

Web Playgrounds of the Very Young;

• 20 million children will be members of a virtual world by 2011, up from 8.2 million today.

Worlds like Webkinz, where children care for stuffed animals that come to life, have become some of the Web’s fastest-growing businesses. More than six million unique visitors logged on to Webkinz in November, up 342 percent from November 2006, according to ComScore Media Metrix, a research firm.

Club Penguin, where members pay $5.95 a month to dress and groom penguin characters and play games with them, attracts seven times more traffic than Second Life. In one sign of the times, Electric Sheep, a software developer that helps companies market their brands in virtual worlds like Second Life and There.com, last week laid off 22 people, about a third of its staff.

By contrast, Disney last month introduced a “Pirates of the Caribbean” world aimed at children 10 and older, and it has worlds on the way for “Cars” and Tinker Bell, among others. Nickelodeon, already home to Neopets, is spending $100 million to develop a string of worlds. Coming soon from Warner Brothers Entertainment, part of Time Warner: a cluster of worlds based on its Looney Tunes, Hanna-Barbera and D. C. comics properties.