This paper provides an overview of five innovative projects involving network learning technologies in the United States: (1) the MicroObservatory Internet Telescope is a collection of small, high-quality, and low-maintenance telescopes operated by the Harvard-Smithsonian Center for Astrophysics (Massachusetts), which may be used remotely via the World Wide Web; (2) the Teaching Teleapprenticeships Project at the University of Illinois is exploring frameworks for learning that use electronic networks to create apprenticeship-like, asynchronous or synchronous learning environments for teacher education; (3) the Learning Through Collaborative Visualization (CoVis) Project at Northwestern University (Illinois) utilizes advanced technologies and innovative pedagogical approaches to help make the teaching and learning of science more like the practices of scientists; (4) the Knowledge Integration Environment (KIE) Project at the University of California at Berkeley has developed a model to foster Web-mediated learning; and (5) the Global Learning and Observation to Benefit the Environment (GLOBE) program is a major Internet-based international science education program aimed to enhance students' understanding of earth systems and to promote science and mathematics learning and environmental awareness. After a brief overview of each project, features common to these projects are discussed, followed by a consideration of challenges to be faced as innovative pedagogies and network technologies are used to support educational improvement and reform. Contains 10 references. (Author/DLS)