This document discusses social media use in federal libraries. It begins with definitions of social media and describes common goals of using social media such as reaching new audiences and increasing awareness of library resources. It also covers federal policies and guidelines regarding social media use. The document then provides examples of different types of social media tools or platforms including social networks, microblogging, RSS feeds, social bookmarking, wikis, photo/video sharing, blogs, and more. For each it gives the definition and examples of federal libraries using that tool. The goal is to help libraries understand how to develop a social media strategy and presence.