1. 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.

  2. Online diagramming application

  3. yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.

  4. Simplify and communicate complex information using data-linked diagrams.

  5. OmniGraffle is for creating precise graphics like website wireframes, an electrical system designs, or mapping out software class.

  6. Dia is a GTK+ based diagram creation program for GNU/Linux, MacOS X, Unix, and Windows, and is released under the GPL license.

  7. Prototyping and collaboration for design teams

  8. PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.

  9. FreeMind is a premier free mind-mapping software written in Java.

  10. Draw, LibreOffice, ODF, open standards, creative software, vector drawing

  11. XMind is a brainstorming and mind mapping application.

  12. Single-user mockup / wireframing / diagramming tool