Here is a very instructional piece from Michael Angeles explaining how to use Excel databases & Visio diagramming software to transform a spreadsheet into a flowchart automatically. It requires some up-front planning & design, but it can be worth it if you make a lot of diagrams. Check out Automating Diagrams with Visio « Boxes and Arrows for the full … Read More
Dia draws structured diagrams
Dia software is a free Windows, Mac OS X and Linux version of the popular open source program. It lets you create flowcharts and diagrams. It also has a library of free shapes to use. You can use these to customize your diagrams.