FreeMind is a premier free mind-mapping software written in java.

Some of the features:

• Fully functional following of HTML links stored in the nodes, be it www links or links to local files.
• From very early versions, Freemind supports folding which is its essential property.
• Fast one-click navigation, including folding / unfolding on one click and following links on one click at the same time (you don’t have to make choice between fast following of links and fast fold/unfold). You can move the map by dragging the map’s background as well as using mouse wheel.
• Undo
• Smart Drag’n Drop, including the possibility to copy nodes or copy style of nodes; dragging and dropping of multiple selected nodes; dropping of texts or list of files from outside
• Smart copying and pasting into, including pasting of links from HTML or structuring the pasted content on the basis of the number of leading spaces in a line; pasting of lists of selected files
• Smart copying and pasting from, including plain text and RTF (MS Wordpad, MS Word, MS Outlook messages).
• Export of map to HTML

Download from here.