All the engineering students and professionals need to draw diagrams of some kind. Dia is just a tool for it. You can draw verious kind of diagrams like entity relationship diagrams, UML diagrams, flowcharts, network diagrams, and many other diagrams.

    It is available for linux as well as windows. As it is open source, source code is also available for download.

Dia is roughly inspired by the Microsoft Visio software, but its free! :)