Console Calculator - Console Calculator is a powerful calculator with a simple console interface.
draw.io - Online diagramming application
SpeedCrunch - SpeedCrunch. SpeedCrunch is a high-precision scientific calculator featuring a fast, keyboard-driven user interface. It is free and open-source software, licensed under the GPL. Download Documentation Donate .
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.
Calculator by Xlythe - Calculator is a simple 4 function calculator.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.