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
CMapsTools
http://cmap.ihmc.us/ IHMC CmapTools program empowers users to construct, navigate, share and criticize knowledge models represented as concept maps
VUE
http://vue.tufts.edu/ is a concept mapping tool to organize, visualize, and present ideas.
XMIND
http://www.xmind.net/
XMind is a concept mapping tool, and a mind mapping tool,
Mind Mapping
FreeMind
is a mind mapping application written in Java
http://freemind.sourceforge.net/wiki/index.php/Main_Page