I recently offered the following workshop for graduate students in our department. The workshop was intended to encourage students to consider a reference management tool to support their research and writing. Zotero is the open source solution that I use and recommend.
Managing Research Workflows: Zotero as an open source option
Abstract: Reference management is a crucially important process and practice for researchers. Building up your library of research articles can help you organize the papers you have read, increase discoverability of your most relevant works, and aid the process of manuscript creation. Many reference management tools can also support file management, the annotation of research articles, and collaborative collections. In this interactive workshop we will explore free tools, such as Zotero, that can support reference management and personal knowledge management as you engage in your research.