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AppMockUp - Create the most compelling screenshots for your app.
draw.io - Online diagramming application
App Store Template - A quick App Store template for Sketch with Presets
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.
AppLaunchpad - Create free beautiful screenshots for App store/Google play
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.