Gaia Online

It’s called Gaia Online,

“The world’s fastest growing online world hangout for teens.”

That’s the way Sherman and his team prefer to characterize Gaia, the brainchild of Studio XD, a comic art firm which gave the site its anime-influenced look. Gaia’s online world aspect (which launches in a separate Java-powered window) is a series of virtual towns where Gaian avatars can socialize (up to 100 in a single space), with apartments they can own, and treasures they can find. (No combat, however.) It’s just that 10% of total user activity takes place in the world itself.
Gold Currency:

A unique innovation is the way the company distributes its virtual gold currency: instead of selling it for real money (as with There) or allowing its trade on the open market (as with Second Life), Gaians are automatically given gold for participation: You get gold for posting on the Forums, for riding events, for uploading content, for exploring the world. Subscribers are rewarded for engaging in Gaia, in other words— and the reward incents them to engage in Gaia even more.

Gold for Auction

With the gold, Gaia subscribers can buy items, clothing, and accessories for their avatars, some sold by the company, but most of it sold via Gaian-to-Gaian auction. (They estimate some 52,000 auctions are completed every day.)

What pays in Gaia, however, stays in Gaia: the company strongly discourages real money trading, and works with Ebay to curtail it. That’s not to say Gaian treasures haven’t been sold online. “One item sold for $6000,” says Sherman. “Wonderful to tell you, but bad for what we’re trying to accomplish.”
More:http://www.gaiaonline.com/