This document provides an overview of libraries and social software. It discusses the evolution from Web 1.0 to Web 2.0 and how libraries are adopting Web 2.0 technologies like RSS, blogs, social bookmarking, and social networking. The document outlines findings from the LASSIE project on how librarians are experimenting with and embracing these new technologies, though staff development challenges remain. Examples are given of libraries using different social software tools and applications.