Package "freeplane"

Java program for working with Mind Maps
Freeplane is a free and open source software application that supports
thinking, sharing information and getting things done at work, in school
and at home. The core of the software is tools for mind mapping (also
known as concept mapping or information mapping) and using mapped
information.

Occupying the middle ground between an editor and a diagramming tool,
Freeplane allows the user to add content as quickly and naturally as they
would in a text editor, yet producing structured content that can be
manipulated as easily as a diagram.

Features include ordering ideas in nodes and freely positionable
nodes, connecting nodes, automatic/conditional styles, scripting,
add-ons, LaTeX, search/filtering, different export features, printing,
password protection of nodes/maps and more.

See http://freeplane.sourceforge.net/wiki/index.php/Main_Page for a full
list of applications and features.