Stickies - Stickies is a PC utility written to replace Post-It-style notes left stuck to your monitor.
draw.io - Online diagramming application
Simple Sticky Notes - Sticky notes have long served a great purpose. Hang them around the home or office and be instantly reminded of important items in your personal or professional life... read more.
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.
Microsoft Sticky Notes - A brand new Sticky Notes for Windows has arrived!
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.