draw.io - Online diagramming application
Elasticode - Build, deploy & personalize native mobile experience
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.
Userlane - Digital adoption platform with interactive guidance for software applications allowing anyone to understand and master any software from the get-go.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
Kompassify - Onboard your users and help them understand your product.