PMM - Personal Memory Manager - Personal Memory Manager helps you spin-off from the top: manage your own knowledge and ideas.
Kialo - Kialo is the platform for rational debate. Empowering reason through friendly and open discussions.
Visual Understanding Environment - Visual Understanding Environment (VUE) is a mind-mapping and concept-mapping tool.
DebateGraph - Graph visualization of: Join a global community of mappers with over half a million ideas and 30,000 maps. Click on the bubbles to explore, and log-in to create free public & private maps on any topic!
Rationale - Rationale let's you create, online, argument maps.
Flying Logic - Highly visual software for planning support used by strategists, process improvement specialists, teachers, and writers. Windows, Mac OS X, and Linux.