Xmind - Xmind is a brainstorming and mind mapping application.
Call to Idea - A gallery of inspiration for product designers
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
AuthorBee - Organize Twitter around your interests
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.
Voynetch - Share your visual notes and graphic recordings.