under 10.6 and previous versions of OS X you could click on the text on the login window and cycle through information about the computer (Serial number, Name, IP, Network accounts, …). This was done away with under 10.7. You regain the ability to retrieve this information from the login window with the below line of BASH:
defaults write /Library/Preferences/com.apple.loginwindow AdminHostInfo HostName
This will need to be run with root permissions, so either use su or sudo to run this in terminal on the machine (i.e. sudo defaults write /Library/Preferences/com.apple.loginwindow AdminHostInfo HostName) or you can send it to a few computers through apple remote Desktop using the unix button. Make sure you choose to have it run as root on the remote computer.
Once you run this on a machine, you can now click on the clock in the upper right hand corner and it will cycle through the computer name, OS Version, and IP Address next to the clock with each click.
I like to give credit that i found this tip on afp548.com[here], it’s not my own creation. But wanted to repost it so that others would hopefully find it helpful.
