project planning

Mindmapping - the birthplace of a great project

There are some fantastic looking mindmapping software products out there, almost all of which offer free trials from which you can make your own judgement and choice.
Mindmapping Software from google

Slowly looking through them:
Open Source solutions include:
XMind - very well developed and accepted software that you can install on your own machine
XMind has a comprehensive free (open source) version and a pro version at very reasonable prices.

Free Mind
An established mindmap environment written in Java that you can install on your own machine

D Richard's html 5 mindmap software looks really good and worth playing with

And a pretty cool lightweight as yet quite small project written Python

And also for your entertainment I can just say I have failed to install the module Graphmind for Drupal because it asked for too many dependencies that I just wasn't prepared to install for it. Maybe in a next life with lots of time on my hands I'll try again.

That's not to say it's bad, just that it's not completely straightforward to install and for the purpose of this site is too time consuming.