Attracted by the break-out success achieved by frontrunners such as Club Penguin and Webkinz (the latter welcoming nearly 12 million unique visitors in March, the most recent month measured by Nielsen Online), a whole new generation of virtual worlds for kids and teens is gearing up to stake out turf on the web. According to a study released last month by Austin, Texas-based Virtual Worlds Management, which puts out a weekly newsletter and runs an annual expo devoted to the subject, there are roughly 60 youth-focused worlds currently operating, with more than 50 others in the pipeline of development and testing.

Tweens (eight to 12) seem to be a natural sweet spot, given that 62 of these virtual world projects cater to them. But kids seven and under are almost as well-served at 52, with the 13 to 18 set bringing up the rear at 44.

It’s worth noting that VWM grouped all of MTV’s virtual worlds as one entry, as it did with most of Disney’s projects in this realm. And with the Mouse House planning nine new hubs and MTV pacing itself at one launch a year, this adds significant weight to the tally.

In development now are worlds based around Ludorum’s Chuggington property, Lego Universe, Spin Master’s Tech Deck toy line, Nickelodeon’s Monkey World and SpongeBob SquarePants, and Ragdoll’s Tronji concept for older kids.

VWM has also released a study revealing that venture capital and media players invested US$184 million in 23 virtual world specialist companies in Q1 2008, with eight of these investments going to youth-targeted projects to the tune of US$16 million. Want to know who’s making and who’s buying? Take a look at the chart above.