draw.io - Online diagramming application
WinWedge - Data collection software for serial devices, including meters, balances, scales or any RS232...
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.
TWedge - TWedge enables you to capture data from devices like bar code readers, scanners, decoders, gauges...
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
NoFlo - NoFlo is a JavaScript implementation of Flow-Based Programming (FBP).