Dia is a full-featured diagramming program. It can be used to draw many different kinds of diagrams and 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.
Dia can load and save diagrams to a custom XML format, can export diagrams to a number of formats including EPS, SVG, XFIG, WMF and PNG, and can print diagrams (including ones that span multiple pages).
Diashapes: You can easily add more shapes to Dia with the Dia Shapes Assistant. It installs alongside Dia and automatically downloads additional shapes you select. Download Diashapes Portable 0.0.1 (2MB download / 2MB installed)