This document discusses creating subject guides for 21st century libraries. It begins with defining subject guides as dynamic resources that help patrons research and explore topics. It discusses how information sources have become more diverse and focuses have shifted to knowing what sources are appropriate. The document outlines basic design principles for subject guides, including incorporating learning models and meaning making. It provides examples of content to include, such as diverse information streams and user-created content. The document also reviews various platforms for creating subject guides and discusses future directions, such as responsive design and participatory technologies.