TiddlyMap - An interactive concept- and mind-mapping plugin for the personal note-taking software TiddlyWiki based on the Vis.js library. It's free and open-source!
Kialo - Kialo is the platform for rational debate. Empowering reason through friendly and open discussions.
Wisdomap - Wisdomap Medicine is a study aid that helps medical students create differential diagnoses and suitable management plans from a presenting complaint and structured revision notes.
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!
IOctopus - IOctopus is an online mind map service for a dive deep into the mind for the best ideas.
Rationale - Rationale let's you create, online, argument maps.