Directory

Free diagramming editor (formerly diagrams.net) for flowcharts, network, UML and architecture diagrams, available as web app, desktop app and integrations

Open-source, outliner-based knowledge base storing notes as local Markdown or Org-mode files with block references, queries and a graph view

Open-source learning management system used by universities and schools for courses, assignments, quizzes, grading and forums, self-hosted or via MoodleCloud