The potential uses of online communication in the preparation of preservice and inservice secondary mathematics teachers transcend the traditional geographic benefits of distance education. Not only can the technology provide asynchronous instruction over great distances, it may also be used to create genuine opportunities for keeping pace with rapidly emerging content, epistemologies, and pedagogical strategies associated with contemporary mathematics. In other words, computational technology is reinventing mathematics while simultaneously increasing opportunities and raising expectations for the learning of mathematics. Mathematics educators will benefit from these technologies via the ability to personally construct mathematics, cope with the rapid pace of mathematical innovation, discuss the pedagogical issues associated with these changes within an expanded community of practice, and learn how technology may be employed to assist more students in a joyful pursuit of mathematical understanding. This paper offers a model for the development of online learning environments designed to prepare new teachers to teach secondary mathematics. The need for dynamic telecourses is discussed, along with features needed to ensure that prospective teachers not only learn new content but pedagogical strategies as well. One current online community, NetAdventure, is offered as a case study of what is currently possible. (Author)