www.microsoft.com Abstract. Collaborative learning is accepted as an effective means of offering students a stimulating and challenging environment where they can learn from each other, at their own pace, through research and questioning. Within a concept-map based learning environment, collaborative projects offer the opportunity for sharing among students in their meaning making and understanding while jointly building concept maps. CmapTools offers a broad range of tools to support collaborative concept mapping. However, we find few cases where meaningful collaborative projects are being carried out between schools. We believe that more technological infrastructure beyond that provided by the CmapServer is necessary to support collaborative concept mapping in schools. In this paper we present LiveMappers.net, a Web-based learning environment integrated with CmapTools that supports concept map-based collaborative projects. LiveMappers offers teachers a set of Project descriptions to choose from and the opportunity to join an Instance or execution of a Project, or teachers can design their own Project and invite colleagues to join. LiveMappers provides each Instance or execution of a project with an environment for students to collaborate supported by Web-based access to shared folders on a CmapServer preset with permissions for sharing among students, the ability to launch CmapTools from those folders to construct and share Cmaps, a common Blog and a Discussion Forum for students and teachers. LiveMappers.net scales up to support thousands of teachers and students participating in collaborative projects.