I am always looking for some good IT cheat sheets, and for a lots of thing. Here is one of my favorite web site around network technologies. Interestingly, this site propose some regularly updated quick reference guides for the network, and are classified under the following categories (at the time of this writing):
You can find them all at the Cheat Sheets Library section.
As the author wrote on his blog, “if you notice an error or would like to see a new cheat sheet on a specific topic”, don't hesitate and drop him a line.