Dia is an open source, multi-platform diagramming software and application developed by the KDE project. It is used for creating diagrams, flowcharts, network diagrams, and other types of technical drawings. It has a user-friendly GUI and supports object-oriented drawing, and is highly extensible with plug-ins and custom shapes. Dia allows for the creation of diagrams containing objects such as boxes, circles, lines, polygons, and text, as well as for the inclusion of images. It also supports a variety of export formats, including .png, .jpg, .svg, .fig, .dia and .xfig. Dia is available for Windows, Mac OS X, and Linux.
Easy to use, no registration (!), complex feature set, very few bugs. Acceptable performance.
Easy to use. Free and open source. Can install it on my PC (linux mint) Better application than Dia, which I can also use online on my PC. very nice!
Easy to use and has all the options you could want. I have now adopted it for the program I have developed in Business Intelligence and Data Analytics.
Feature Reliable and extendable.
It is not a GUI diagramming tool. By this logic, Graphviz is an alternative to Dia.
Suggesting Vector would be the same as suggesting Photoshop. Just because you can draw pictures and use them to create a flow doesn't mean it's a diagram or flowchart-centric application.
Intuitive interface, good rendering, web-based, so it can be used both locally and on a website
Draw.io is very useful, with an elegant interface, tons of templates/shapes and the ability to export to various file formats. I've used it for home and work projects and am pleased with the results. I would even go so far as to say it is more useful than MS Visio if your requirements are not too technical.