Dia - Main window
Dia allows you to draw many different kinds of diagrams. It has special objects to help you to draw entity relationship diagrams, UML diagrams, flowcharts, network diagrams, etc. It is also possible to add support for new shapes by writing simple XML files.
It can load and save diagrams to a custom XML format (gzipped by default, to save space), export diagrams to EPS, SVG, XFIG, WMF and PNG, and print diagrams (including multiple pages ones).