Software for creating flowcharts, UML diagrams etc.
Online card game for an easy introduction to threat modeling
Open source online editor providing collaborative editing in real-time
Collaborate to sketch diagrams that have a hand-drawn feel to them
Real-time collaborative markdown note editor
Open source, collaborative online LaTeX editor, also known as "ShareLaTeX"
Online whiteboard for collaborative work with virtual post-its and index cards
Kanban board for card-based task management