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.
InVision Studio - The world’s most powerful screen design tool
draw.io - Online diagramming application
Paste by FiftyThree - Show your work. Paste is a new presentation tool for Slack.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.