Neuronstorm [L1 ] is a free, open source program for creating mind-maps - pictorial representations of a central idea and how it is linked to other ideas or concepts.
Neuronstorm is also designed to be compatible with and eventually replace Inspiration(TM) - a commercial mind-mapping program.
The Neuronstorm team invites developers, graphic designers and potential users to help. See the Community Portal for more information.
Neuronstorm uses Tcl as its scripting language and, at present, saves files as Tcl commands.
The release blurb at the author's blog is here [L2 ]