JSON Generator - Create mock and sample JSON using a powerful template syntax
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.
Mockaroo - A realistic data generator to test your app
draw.io - Online diagramming application
Ideas Are Worthless - Like Product Hunt. But for Ideas.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.