Average score 3.28 (based on 53 votes)given by Steve Leonard on January 22, 2007  
 given by Mihai Campean on January 26, 2007  
 given by Mike on January 27, 2007  
 given by Anonymous on January 28, 2007  
 given by Anonymous on February 22, 2007  
 given by Anonymous on June 10, 2007  
 given by DC on January 31, 2008  
 given by Anonymous on February 21, 2009  
 given by Anonymous on June 7, 2011  
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You create a central circle with a word in it, and off that you have rectangle nodes, each of which can have child nodes. You can have "graphical links" (ie arrows) between nodes and clouds to group related items.
It does a lot though I might have like to be able to link a child node to 2 parent nodes, which is not possible.
Good free tool though. I now use it for my daily and weekly to-do list.