draw.io - Online diagramming application
FlippingBook - FlippingBook changes the way you present your documents
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.
Scribd - Unlimited books, audiobooks & comics. Unparalleled discovery. Any device. $8.99/month
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
Flipsnack - Flipsnack | PDF to HTML5 flipbooks