Dia is designed to be much like the commercial Windows program ’Visio’. It can be used to draw many different kinds of diagrams. It currently has special objects to help draw entity relationship diagrams, UML diagrams, flow charts, network diagrams, and simple circuits. It is also possible to add support for new shapes by writing simple XML files, using a subset of SVG to draw the shape.
It can load and save diagrams to a custom XML format (gzipped by default, to save space), can export diagrams to EPS or SVG formats and can print diagrams (including ones that span multiple pages).

Website: http://live.gnome.org/Dia

download: http://dia-installer.de/index_en.html (12.2 MB for windows)

Pre-requisites

Dia needs the GTK+ Runtime Enviroment version 2.10 or higher (included in the installer).

Tool Features

Draw on canvas
- Rectangle/Square/Box
- Line
- Oval/Circle/Ellipse
- Connector lines
UML Support
Saves in XML format.
Supports export to most of the image formats including SVG.
Develop multi layered diagram multi layered.
Available for Windows and Most of Linux version
includes Visio VDX import and export
Create any kind of diagrams like UML, Network Diagram, and Flow Chart are just few to name.