CmapTools is a software suite that facilitates the collaborative construction, sharing and publishing of knowledge models represented as concept maps. CmapTools is used worldwide by millions of users, and is available in over 15 languages. Users of all ages, from elementary school children to NASA scientists and other professionals use CmapTools to express and share their understanding about any topic. Based on a client-server architecture, CmapTools facilitates both synchronous and asynchronous collaboration during the construction of concept maps through CmapServers where concept map-based knowledge models are shared and published as Web pages. The software runs on all hardware/software platforms (Windows, Mac OS X, Linux, etc.) and is available for free download. To help users learn about concept mapping and its uses, IHMC has also developed the Cmappers.net site.