Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
Xmind - Xmind is a brainstorming and mind mapping application.
Standard Notes - A safe place for your notes, thoughts, and life's work
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
FeatureMap - FeatureMap story mapping, simple and effective realtime collaboration and collective intelligence tool.