An Internet forum is a web application for publishing user-generated content under the form of a discussion. Messages posted to the Internet forum form threads of discussion and contain textual and multimedia contents. An important feature of Internet forums is their social aspect. Internet forums attract dedicated users who build tight social communities. There is an abundance of Internet forums covering all aspects of human activities: politics, sports, entertainment, science, religion, leisure, hobbies, etc. With large user communities forming around popular Internet forums it is important to distinguish between knowledgeable users, who contribute high quality contents, and other types of users, such as casual users or Internet trolls. Therefore, social role discovery becomes an important issue in discovery of valuable knowledge from Internet forums. This chapter provides an overview of Internet forum technology. It discusses the architecture of Internet forums, presents an overview of data volumes involved and outlines technical challenges of scraping Internet forum data. A broad summary of all research conducted on mining and exploring Internet forums for social role discovery is presented. Next, a multi-tier model for Internet forum analysis (statistical analysis, index analysis, and network analysis) is introduced. Social roles are automatically attributed to Internet forum users based on egocentric graphs of user activity. The issues discussed in the chapter are illustrated with real-world examples. The chapter concludes with a brief summary and a future work agenda.