Concept maps are an effective way of representing a person’s understanding of a domain of knowledge. Technology can further help by making it easy to construct and modify that representation, to manage large representations for complex domains, and to allow groups of people to share in the construction of the concept maps. CmapTools is a software environment developed at the Institute for Human and Machine Cognition (IHMC) that empowers users, individually or collaboratively, to represent their knowledge using concept maps, to share them with peers and colleagues, and to publish them. It is available for free for educational and not-for-profit organizations, and public servers have been established to promote the sharing of knowledge. The client-server architecture of CmapTools allows easy publishing of the knowledge models in concept map servers (CmapServers), and enables concept maps to be linked to related concept maps and to other types of media (e.g., images, videos, web pages, etc.) in other servers. The collaboration features enable remote users to asynchronously and/or synchronously collaborate in the construction of concept maps, and promote comments, criticism, and peer review. Public CmapServers have resulted in a large collection of knowledge models publicly available, constructed by users of all ages in a variety of domains of knowledge and from a large number of countries.