draw.io - Online diagramming application
GraphThing - GraphThing is a tool that allows you to create, manipulate and study graphs.
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.
JFLAP - JFLAP is software for experimenting with formal languages topics including nondeterministic finite...
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.
Rocs - Rocs aims to be a Graph Theory IDE for helping professors to show the results of a graph algorithm...