Dia – Diagram Creator is a free open source diagram creation program released under the GPL license. The functionality Dia diagram software similar to Visio. It can be used to draw many different kinds of diagrams such as entity relationship diagrams, UML diagrams, flowcharts, network diagrams, simple circuits and much more.
Dia can print diagrams that span multiple pages, export to many formats (EPS, SVG, CGM and PNG), and the ability to use custom shapes created by the user as simple XML descriptions.
The Tools menu simply provides menu access to all of the tools located on the upper area of the main window. Dia supports the Universal Modeling Language (UML) includes the entire static structure diagram elements specified in the UML specifications. The DIA diagram sheet includes, in order, a Class, Template Class, Note, Dependency and Realization
To install Dia on Windows, you needs the GTK+ Runtime Enviroment version 2.6 or higher. GTK+ Runtime Environment 2.8 is available from download here.