draw.io - Online diagramming application
Revue - The easiest way to create and send a curated newsletter
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.
Substack - Substack makes it simple for a writer to start an email newsletter that makes money from subscriptions.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
Postie - Email campaigns built for you using your best social content