Xmind - Xmind is a brainstorming and mind mapping application.
Novelize - Novelize is an online novel writing app designed to keep authors on track.
FreeMind - FreeMind is a premier free mind-mapping software written in Java.
BlankPage - Stay motivated to write, and finish your story
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Manuskript - Open-source tool for writers.