This article contains a description of a network-based Learning Environment Organizer entitled LEO, which takes its impetus from the Assimilation Theory of meaningful learning. LEO represents a new approach to computer-mediated augmentation of face-to-face, or hybrid courses, and a different approach to distance learning course delivery. LEO provides the learner with a graphical advance organizer for the course, links to instructional content, various completion criteria for topics, and a visual representation of student progress. The organizer is non-linear in the sense that it maps only those prerequisites that are necessary for any given topic, creating many potential paths through the material. LEO is part of a software suite entitled "CmapTools" that provides a unique method of knowledge modeling or instructional content structuring. LEO can be used to organize CmapTools-type knowledge models or any other online instructional content. This work presents a description of the software's rationale, basic functionality, look and feel, and a discussion of an example course organizer.