Adobe XD - Adobe XD is an all-in-one UX/UI solution for designing websites, mobile apps and more.
draw.io - Online diagramming application
Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
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.
Slack - A messaging app for teams who see through the Earth!
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.