Kinopio - Thinking canvas for mind mapping, brainstorming, and moodboards
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.
Kanboard - Kanboard is a free and open source Kanban project management software.
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.
Excalidraw - Excalidraw is a whiteboard tool that lets you easily sketch diagrams that have a hand-drawn feel to them.
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.