BlankPage - Stay motivated to write, and finish your story
draw.io - Online diagramming application
Novelize - Novelize is an online novel writing app designed to keep authors on track.
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.
Manuskript - Open-source tool for writers.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.