The purpose of the book is to set up a framework for discussions on social and technical issues of online communities. Designing usability and supporting sociability lays a solid foundation on which online communities can grow and thrive. Intended for both students and computer professionals, the book addresses the development of new online communities as well as the improvement of existing ones. It is divided into two parts -- Getting Acquainted with Online Communities and Developing Online Communities -- along with a preface and a concluding chapter which explores the future of online communities. For sample chapters and other resources, please check out the web site for the book at www.ifsm.umbc.edu/onlinecommunities.