Source: http://lifehacker.com/#!5795870/diagramly-is-a-quick-online-diagram-mind-map-and-flow-chart-creator
There are plenty of apps for creating flow charts, mind maps, and other types of diagrams, but Diagramly is ready to go the minute you visit the site. It's remarkably similar to Microsoft Visio, but it's accessible from pretty much any web browser and doesn't even require signing up.
If you've ever used Microsoft Visio, or pretty much any diagram-creating software, Diagramly should feel pretty familiar. Your shapes, text, and icons onto your grid, name them, and connect them with arrows. While there are plenty of webapps that rival desktop software, a lot of the graphics-based apps have a bit of lag. Diagramly is, fortunately, very responsive. It saves out to several image formats and allows you to print directly from the app. It's actually a really solid replacement to desktop diagraming software.
Diagramly is available for free, and all you have to do is go visit the site to get started.
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