Today the Internet plays a role in the lives of nearly 40% of the world's population, and it is becoming increasingly entwined in daily life. This growing presence is transforming psychological science in terms of the topics studied and the methods used. We provide an overview of the literature, considering three broad domains of research: translational (implementing traditional methods online; e.g., surveys), phenomenological (topics spawned or mediated by the Internet; e.g., cyberbullying), and novel (new ways to study existing topics; e.g., rumors). We discuss issues (e.g., sampling, ethics) that arise when doing research online and point to emerging opportunities (e.g., smartphone sensing). Psychological research on the Internet comes with new challenges, but the opportunities far outweigh the costs. By integrating the Internet, psychological research has the ability to reach large, diverse samples and collect data on actual behaviors, which will ultimately increase the impact of psychological research on society.