Xmind - Xmind is a brainstorming and mind mapping application.
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.
FreeMind - FreeMind is a premier free mind-mapping software written in Java.
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.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.