Dia is an open-source program that allows one to easily create diagrams and flowcharts. Rivaling Microsoft Visio, it’s free and easy to work with. It has more than a dozen templates that allow you to grab some pre-made shapes including computers, electrical, logic, CISCO, isometric maps, and flowchart icons. It’s a light-weight application that’s just nice to keep handy.
You can drag shapes or click them to their location. Draw lines to connect objects and navigate very easily. All together, Dia is a very polished project that completes its goal without being bloated and hogging-resources. If somebody is looking for Visio or another diagramming application, I would recommend that they give Dia a look. It can open Visio XML files (.vdx), Drawing Interchange (.dxf), and many more (.jpg, .gif, .svg, .wpg) along with its own (.dia). From experience, it’s great for students for the demands and the price.
http://dia-installer.de/index_en.html