From Gaia, a Japanese anime-inspired site, to vSide, a hip nightclub scene, they represent the latest way people are interacting through the Internet. Users create alter-ego avatars to navigate these online worlds, where they meet and hang out with other people, go shopping, watch movies, even start a business.

And they're live: Day and night, they change as people join in.

Though the idea is not new, the technology and the business to support these virtual worlds are starting to catch up. And now a new generation, inspired in part by Linden Lab of San Francisco's Second Life, is starting to evolve.