yEd is a free general-purpose diagramming program with a multi-document interface.

PlantUML is an open-source tool allowing users to create UML diagrams from a plain text language.

Lovely Charts is an online diagramming application that allows you to create professional looking diagrams, such as flowcharts, sitemaps, organisation charts,…

Diagramo is an online flowchart software. It's FREE and Open Source ( GPL ) It's pure HTML5 Share and collaborate.

Creately is a collaborative diagramming and design software used by teams around the world to communicate more effectively.

Gliffy is software for diagramming via a HTML5 cloud-based app. It is used to create UML diagrams, floor plans, Venn diagrams, flowcharts and various other ki…

Storyboard That is a free online storyboard creator.

ProcessOn is an easy-to-use, free and powerful online diagram designer which support to share and real-time collaboration.