diagrams.net (formerly called Draw.io) is a completely free, open-source, cross-platform and stand-alone flowchart drawing application that can be used as a browser-based web application, desktop application and plug-in for some other software. That's to say, you can use its web edition directly in a web browser (no registration required, no limitations, no catches), or use its desktop edition offline under Windows, Mac or Linux OS.

Mind mapping software is a very good thinking management tool, which is pretty practical in organizing work ideas, simplifying work flow, making meeting minutes, performing tasks management, time management, and many other aspects. Nowadays, many companies and individuals start learning and using mind map, because it can help us spread our minds, get our ideas into shape, then improve our work efficiency and simplify the entire work flow.

Dia (full name: Dia Diagram Editor) is a vector-based and Visio-like structured diagram drawing tool made by Alexander Larsson from Germany. It's lightweight, free to use and open-source, supports for Windows, Mac OS X and Linux.