From the webpage:
MindMup is a zero-friction mind map canvas. Our aim is to create the most productive mind mapping environment out there, removing all the distractions and providing powerful editing shortcuts.
This project is relatively stand alone and you can use it to create a nice mind map visualisation separate from the MindMup Server.
Do see the live demo at: http://www.mindmup.com.
It may not fit your needs but it is a great demo of thoughful UI design. (At least to me.)
Could be quite useful if you like The Back of the Napkin : Solving Problems and Selling Ideas with Pictures by Dan Roam.
I recently started reading “The Back of the Napkin,” and will have more to report on it in a future post. So far, it has been quite a delight to read.
I first saw this at JQuery Rain under: MindMup MapJs : Zero Friction Mind Map Canvas with jQuery.