Web-based distance learning researchers, technology designers, and practitioners (i.e., course developers and instructors) have been on a quest to construct online environments that satisfy a wide range of cognitive, pedagogical, motivational, and social goals while overcoming a range of practical constraints (e.g., temporal, geographical, technological, ﬁnancial, and organizational). The U.S. Department of Education program that sponsored the symposium leading up to this volume-Learning Anytime, Anywhere-conveys one category of goals: overcoming practical constraints of temporal or geographical copresence, or both. The focus is to design environments that (a) increase the availability of learning experiences to learners who cannot or (for many reasons) choose not to attend traditional face-to-face offerings, (b) assemble and disseminate instructional content more cost-efﬁciently, or (c) enable instructors to handle a larger number of students. These goals are justiﬁable in their own right, and technology designers, as reﬂected in this volume, have done an excellent job building delivery platforms to meet those goals. At one end of the continuum are technologies that support asynchronous communication only, such as threaded discussion boards and newsgroups, which enable users to contribute at their own convenience (e.g., Duffy & Kirkley, Chap. 6, this volume; Shea, Fredrickson, & Pickett, Chap. 14, this volume). At the other end are technologies designed to recreate copresent teaching strategies, such as delivering lectures and holding discussions with both large and small groups of students (e.g., Webcasting, whiteboards, chat rooms, and desktop video technology, which are used to deliver lectures and hold discussions with large and small groups of students; e.g., Ruhleder, Chap. 4, this volume; Polin, Chap. 2, this volume).