Just a few years ago, virtual worlds were credited with the power to transform the universe. Used since the late 1990s in military and medical applications, virtual worlds first gained mainstream media attention when Linden Lab released Second Life in 2003. While other worlds, including open source environments, have launched since then (examples include OpenSim, Blue Mars, Open Wonderland, Open Cobalt, and Unity), Second Life remains the largest general-purpose virtual world--with its own currency, Linden dollars, which can be used to buy, rent, or trade land and goods. Yet, in the eight years since its debut, Second Life has lost much of its vitality. Most commercial companies have quit their virtual world operations. A recent survey by the Pew Internet & American Life Project found that only 8 percent of online teens and 4 percent of online adults visit virtual worlds. And, after an initial rush to set up campuses in Second Life, many colleges and universities are quietly tapering off their usage. Some say the virtual real estate bubble has burst, but next-gen technologies and niche applications may breathe new life into virtual environments. (Contains 1 online resource.)