I have looked around the Internet several times for something that looks like a piece of software equivalent to Microsoft Visio, able to run on Ubuntu. ASCII drawing just dont work for me..
It's in the cloud
I will leave this post open for others to comment on, and I believe I will update it whenever I stumble upon some great piece of software. Until then, you could take a look at Gliffy. It's similar to pixlr.com, which means that you do all the drawing in your web browser. It actually worked quite well. I did some semi-advanced network diagrams, with the usual server components etc. It's all drag-n-drop, with text options, coloring and all what you expect. My environment? Ubuntu 11.10 and Opera.
Theres a hitch. It's not free. You do get a 30 day free trial, and I did some really good drawings and managed to save as PNG when finished. After the trial it costs $4.95 per month, which actually is not that bad. And compared to Microsoft prices, it's really good.
So what can I say? I will probably not use it that much, and I don't have the need to save to .vsd. But nevertheless, it beats pasting .jpg icons in an excel sheet or whatever we have in the Linux world. So give it a try, draw some fancy network diagrams with switches, servers, proxy's with your own layout and colors. Give it a try at www.gliffy.com. If you find something similar (or installable), please post a comment..