Dia an opensource money saving alternative software created by Alexander Larsson designed to be one of the best free options for 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, UML , flow charts, UML and 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.

Some highlights features that we could find are:

  • It is easy to learn and flexible enough to allow power users to create highly customized diagrams
  • One important feature is that it can load and save diagrams to a custom XML format which will be gzipped by default, to save space.
  • It is able to import and export the following file types:
  • Scalable Vector Graphics (.svg) AutoCad Drawing eXchange Format (.dxf) Visio XML File Format (.vdx) XFig File Format (.fig) GdkPixbuf bitmap graphics (.bmp, .gif, .jpg, .png, .pnm, .ras, .tif)
  • It supports exporting to numerous formats for excellent web publishing. Some of them include:
  • Computer Graphics Metafile (.cgm) Dia Shape File (.shape) HP Graphics Language (.plt, .hpgl) Encapsulated Postscript (.eps, .epsi) Postscript (.ps) Portable Document Format (.pdf) Portable Network Graphics (.png) TeX Metapost macros (.mp) TeX PSTricks macros (.tex) WordPerfect Graphics (.wpg) XFig format (.fig) XSLT (eXtensible Stylesheet Language Transformation) (.code)

You could get it for free from the Dia Website, you can also download additional files to make it more useful. Also the developers gives you the option to use it online, no registration required.