blockdiag!

yEd is a powerful diagram editor that can be used to quickly create diagrams manually or import external data for analysis and auto-magically arrange even large data sets by just pressing a button. You can use yEd to quickly create flow charts, BPMN and UML diagrams, organization charts, mind maps, and many other kinds of diagrams, graphs, and networks. Choose from a wide range of highly sophisticated layout algorithms to automatically arrange diagrams in no time. An intuitive and visually appealing user interface makes creating diagrams fun. Once a diagram has been created, it’s easy to save, print, or export it to popular formats like PDF, SWF, EMF, SVG, JPEG, GIF, PNG, or HTML image maps. »

PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams. The generator can be run anywhere within JVM and integrated with various application such as wiki, text editor, IDE, programming language, documentation generator, and others. Mostly based on Graphviz. Can render various diagram syntax such as PlantUML, Dot, and Ditaa.

Graphviz is open source graph visualization software. It has several main graph layout programs. It also has web and interactive graphical interfaces, and auxiliary tools, libraries, and language bindings.

Gephi is an open-source software for visualizing and analyzing large networks graphs. Gephi uses a 3D render engine to display graphs in real-time and speed up the exploration. Use Gephi to explore, analyse, spatialise, filter, cluterize, manipulate and export all types of graphs.

Diagrammix is a tool for efficiently building attractive diagrams.

Delineato - the italian word for "outline". Designed using the WYSIWYN paradigm - What You See Is What You Need - this carefully crafted application is targeted at creating simple diagrams, mind maps, brainstorming, to-do lists, architectural diagrams.A clutter-free interface allows you to concentrate and focus on the essence of your work.

KeyLines is a JavaScript toolkit used by developers to build powerful network visualization applications, quickly.

As the easiest way to explore graph data, Linkurious technology helps you make sense of your data through a simple web-based interface. Companies can quickly visualize their data with Linkurious Enterprise or build their own application with the Linkurious SDK:

Neoclipse is a standalone workbench application to interact with Neo4j (database directory or server). It supports Cypher, index searches, visualisation, graph updates.

Ever wanted to simplify documentation and avoid heavy tools like Visio when explaining your code? This is why mermaid was born, a simple markdown-like script language for generating flowcharts, Gantt charts and sequence diagrams from text via JavaScript.

Create weighted and unweighted graphs and run algorithms step by step. Learn graph theory interactively… much better than a book!