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.
It 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 (including ones that span multiple pages).
Dia is available to download for Windows and Linux. The tutorial even explains how to download and install for each operating system.
The Industrial Engineer can really use Dia for a number of projects. Just to name a few include flowcharting process flows, diagramming models of queues, and mind mapping exercises.
The BeginningLinux.com tutorial does a great job of detailing the steps to get projects started. I find that tutorials with pictures or screenshots tend to be the best. This tutorial has plenty of screenshots to guide the beginner diagrammer.
As I have mentioned before there are great alternative IEOR Tools available in the free and open source community. Give Dia a try and let me know about your experience.