GitHub is the world’s largest collection of open source software, with around 27 million users and 80 million repositories. These numbers make GitHub an invaluable source of data for large-scale empirical software engineering research. In this talk, we describe recent research conducted in our group, based on GitHub data. For example, we are using GitHub to predict the popularity of open source projects, to understand the motivations behind refactoring, to characterize the evolution of APIs, and to reveal key characteristics of open source development teams. In the talk, we also plan to discuss the strategies we are using to make our research results known by practitioners.