The Virtual Worlds Exploratorium is a multidisciplinary project dedicated to the study of communication-related behaviors using data from massively multiplayer online games (MMOs). In a partnership with a corporation that hosts an MMO, a 20-person team of scholars is engaged in the study of behavior within a game and also game activities that parallel those in "real life" (e.g., economic activity, social networking, group processes). A key aspect of our approach is a unique multidisciplinary collaboration of social and computational scientists to help advance the state of the research. This article discusses the methodological, measurement and organizational challenges of the project, the game, the data, and several representative research streams. It also articulates several measurement issues that the research team has faced in order to provide best practices and lessons learned for others considering similar investigations.