Scribble Online Whiteboard - Scribble Online Whiteboard is an advanced collaborative whiteboard solution that allows you to draw the sketch using the web-based or mobile platforms such as iPad/iPhone and Android.

Freeplane - Freeplane is a powerful and free software for building mind maps.

Ryeboard - A practical and visual workspace for modern teams

Linked Ideas - A macOS/iOS apps to treat ideas as links of concepts.

Whiteboard Team - Draw, explain and collaborate visually in real-time.

vym - VYM (View Your Mind) is a tool to generate and manipulate maps which show your thoughts.