Dia is a drawing and diagramming application for Linux or Windows.
I have used it for a long time to draw network and flow diagrams for my work.
However I’ve always been a bit whelmed of the under variety, by the 2 dimensional icons for some things. While there is a huge number of very cool Cisco icons. If you are wanting to do one of those cool Visio style diagrams with the Orthogonally projected icons there wasn’t the correct shapes in dia to use. Until now. This guy has converted some Gnome icons into dia shapes which provide quite handsome network icons. Go to his blog and follow the download link. Follow the instructions to install.
Here is a sample: