Fully navigable online worlds are flourishing, and all that virtual real estate needs to be furnished. Fantasy worlds such as Linden Labs' Second Life and even reality-based environments such as Google Earth are built to accommodate user-generated houses and other objects, which anyone can design using in-game tools or Google's SketchUp 3-D modeling software. But if you want a modernist masterpiece on your plot of virtual land, you don't have to build it yourself. Several companies and hundreds of individuals have gone into business as virtual contractors, designing items and structures that they can sell for real-world cash.

The group most fully integrated into Second Life is Electric Sheep of Washington, DC, whose 11 designers and developers can build anything from a stately pleasure dome to an entire interactive island. For the New Media Consortium, a not-for-profit group of more than 200 teaching organizations with a focus on new media technologies, the company designed and built such an island, where the consortium held virtual classes and events attended by the digital "avatars" of people around the world.