If you are looking for an alternative to Microsoft Visio that is simple and free, take look this Dia Diagram Editor, a free drawing tool for structured diagram.
It’s got all the basic shapes needed for drawing a structured flowchart. All shapes have the text block built-in with a lot of connecting points for connectors. It also has all kinds of connectors for you to choose, lines, arcs, polylines, etc.. All connectors can be associated with the drawing shapes.
Dia also supports Layers so you can put different drawings to the different layers to toggle them between show and hidden.
The drawing drawn in Dia can be exported to a wide range of other formats, including the Visio XML file format .vdx. But unfortunately, it doesn’t seem to be able to open the standard Visio file format.
Dia is certainly a great tool for those who are looking for a good alternative to Microsoft Visio which isn’t free. Even though it only covers a portion of what Visio can do, it does very well and is mostly sufficient for drawing a structured diagram.