Iconosquare - Schedule now. We'll post on Instagram for you later!
draw.io - Online diagramming application
Storyheap - Manage your SnapChat and Instagram stories.
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.
Later - Schedule and manage your Instagram posts
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.