Lax.js - Create beautiful & smooth animations when you scroll
draw.io - Online diagramming application
ScrollMagic - The jQuery plugin for magical scroll interactions.
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.
ScrollReveal - ScrollReveal is a tool to add scroll animations for web and mobile browsers.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.