Mind mapping software is used to create diagrams of relationships between ideas or other pieces of information. A concept map is a special form of a web diagram for exploring knowledge and gathering and sharing information
Concept and Mind Mapping Software
http://compendium.open.ac.uk/institute/ is a knowledge and concept mapping tool.
Compendium is about sharing ideas, creating artifacts, making things together, and breaking down the boundaries between dialogue, artifact, knowledge, and data
http://cmap.ihmc.us/ IHMC CmapTools program empowers users to construct, navigate, share and criticize knowledge models represented as concept maps
http://vue.tufts.edu/ is a concept mapping tool to organize, visualize, and present ideas.
XMind is a concept mapping tool, and a mind mapping tool,
is a mind mapping application written in Java