CKEditor - Real-time collaborative future-ready rich text editor
Xmind - Xmind is a brainstorming and mind mapping application.
Summernote - Summernote is a JavaScript library that helps users create WYSIWYG editors online.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
Froala Editor - Froala Editor is a WYSIWYG HTML editor that enables rich text editing capabilities for the applications.
Coggle - Coggle is a simple, beautiful, powerful way of structuring information.