Kanboard - Kanboard is a free and open source Kanban project management software.
Meistertask - MeisterTask is an intuitive task management and collaboration tool.
Excalidraw - Excalidraw is a whiteboard tool that lets you easily sketch diagrams that have a hand-drawn feel to them.
Kanbanchi - Based on kanban, a scheduling system that originated in Japan, Kanbanchi lets teams collaborate in a drag-and-drop environment that enables reviewing multiple projects' highlights on one screen... read more.
Kinopio - Thinking canvas for mind mapping, brainstorming, and moodboards
KanbanFlow - KanbanFlow is a Lean project management tool allowing real-time collaboration between team members. Supports the Pomodoro technique for time tracking.