draw.io - Online diagramming application
sn0int - sn0int is a semi-automatic OSINT framework and package manager
LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
Lampyre - Lampyre - an efficient data analysis and OSINT multi-tool for everyone.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
SIREN.io - Siren is an investigative intelligence platform.