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Diagram your network with these tools

For really simple diagrams how about www.simplediagrams.com

It would be nice if you could just add which OS they use, Linux, OSX and Windows.

While not specifically a Network Diagram tool it can be used for that. It's main advantage is the display of linked graphs like network diagrams. The data format is XML, a format called graphml.
The editor is Java based and FREE.
http://www.yworks.com/en/products_yed_about.html

plus Kivio on Linux machines, which can use Dia graphics in addition to its own, and possibly others as well.

Wait... you want ME to use a tool to DRAW a diagram of a network? Don't be silly.

I am running a computer on the network. Let the lazy thing discover what is on the network itself and let IT draw the diagram! In the meantime, doing this may actually be productive, IF it is be able to show me where my network is broken.

Where's my suntan lotion?

If you don't need to diagram a network, and you aren't in charge of a network, why would you need to diagram a network? I suppose everyone on the TV speaks directly to you, issuing commands, as well?

Also, this has absolutely nothing with network auto-discovery features of operating systems and network hardware.

Everybody on the TV speaks directly to me.

But that doesn't mean I can draw or draw a network properly or accurately.

I paid all of this money to get computers to work FOR me.

"Oh computer,...computer....(picks up mouse and speaks into saying)...computer...a Keyboard..how quaint!"

Why is everyone having a dig at ddally? I think what he is saying is that there are tools out there that will auto-discover (much of) your network and make the job of documentation much, much easier.
Not all of us enjoy the luxury of good documentation. I am a contractor and have walked into jobs with extreamly complicated networks were the only documentation existed in the previous encumbant's head (probably why they were "previous").
If there are tools that give you a head-start on the mapping process why not use them?

Solarwinds have a nice tool called LANSurveyor.
It uses SNMP and pings to map your network and will span network (just specify the IP range).
LANSurveyor Express is a free download from Solarwinds and works automatically with Visio 2007 to draw an acceptable map.

Gee, maybe some of the more successful among us diagram and document our networks (or parts thereof) _before_ implementation (good luck auto-discovery ;-)). An excellent method to give yourself a chance at recognizing/correcting problems before they occur.

Another diagramming tool can be MaSSHandra. It creates network diagrams in 3D

I was looking for how to make vehicular networking diagram and found it with Conceptdraw pro. I must say that I'm very impresed with this product.
They call it solution park, where you can find samples and videos of what you can do with concept and updates for network diagramming drawings.

I've been using Visio and ConceptDraw. Visio was always a standard tool for us and we just got used to it. However I was looking for a better templates and mac support. Firstly I've faced ConceptDraw 7 which was an interesting alternative but not very stable. Thankfully to their support I stayed with this product. Now I'm using version 9 and that's a big breakthrough in diagramming that gave me a stable product. I'm also surprised with their update policy, they release free updates with lots of cool stuff almost every month.

I checked out some of the links from the list, and none of them were free: they were just free trials for products which did not specify the trial limitations. Like: can I no longer open the product after 21 days? Can I save my work in another format first then, which I can open/view with another product then? I don't download trials which don't specify the trial limitations, because I don't like to waste my time/work.