Dia is a free Open Source diagram maker which aims to provide the kind of flow and org chart loveliness that’s missing from your life. It was ‘roughly inspired’ by Visio (a darn fine product!) which makes for a good start. The latest version imports from Visio files and exports to just about any format you’ll need. Definitely worth a look.
Dia is roughly inspired by the commercial Windows program ‘Visio’, though more geared towards informal diagrams for casual use. It can be used to draw many different kinds of diagrams. It currently has special objects to help draw entity relationship diagrams, UML diagrams, flowcharts, network diagrams, and many other diagrams. It is also possible to add support for new shapes by writing simple XML files, using a subset of SVG to draw the shape.