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.
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
Ryeboard - A practical and visual workspace for modern teams
Invision - Prototyping and collaboration for design teams
Whiteboard Team - Draw, explain and collaborate visually in real-time.
Sketch - Professional digital design for Mac.