From IFORS Developing Countries OR Resources
yEd is a powerful desktop application that can be used to quickly and effectively generate high-quality diagrams. Create diagrams manually, or import your external data for analysis. Our automatic layout algorithms arrange even large data sets with just the press of a button.
yEd is freely available and runs on all major platforms: Windows, Unix/Linux, and Mac OS X.
Link to website: https://www.yworks.com/products/yed