Dia for Windows

Dia is free open source general-purpose diagramming software, inspired by the commercial Windows program “Visio”, though more geared towards informal diagrams for casual use.
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.
Dia can load and save diagrams to a custom XML format (gzipped by default, to save space), can export diagrams to a number of formats, including EPS, SVG, XFIG, WMF and PNG, and can print diagrams.

Dia for Windows