Communities of Practice (CoPs) are informal groups people form around shared problems or disciplines. As natural drivers of knowledge-sharing and innovation, they are the cornerstone of Knowledge Management programs, and are viewed by organizational scholars as a key element of the knowledge-based view of the firm. Nowadays, employees and organizations face considerable turmoil from phenomena such as globalization, rapid technological change, and the increasingly mobile workforce. This hinders employees from regular engagement in face-to-face CoPs, thus increasing the need for virtual CoPs that engage effectively over the Internet. This book reports a systematic search for Usenet-based CoPs that displayed all the traits of co-located CoPs as described in seminal studies. The study used surveys and content analyses as measurement instruments, and found four fully compliant virtual CoPs. The implication for employees is that they can enhance their professional skills through virtual CoP engagement. Organizations, in turn, can foster this engagement in extra-organizational CoPs to tap the rich knowledge ecologies in which businesses work today and keep abreast of fast changing fields.