Erik is doing a workshop which requires Skype.
I have pushed the installer to all Lab B machines, and can install it silently from the Ghost console with this command:
c:\documents and settings\administrator\desktop\skypesetup.exe
and the following parameters:
/verysilent /sp-

If we want to remove the link added to the desktop, then do:
del "c:\documents and settings\all users\desktop\skype.lnk"

UPDATE: Skype does not need to have a global firewall exception to work. It should, however, have a registry setting applied that denies it supernode powers. The file looks like this:

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Skype]
[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Skype\Phone]
"DisableSupernode"=dword:00000001

The reg file and other info on Skype in an educational settings was pinched from here: https://www.cs.uwaterloo.ca/twiki/view/CF/SkypeConfiguration
and here:
http://its.ndsu.edu/security/it_security/index/skype_use_at_ndsu/

Something to investigate if we deploy Skype on all lab machines (at least in Windows) is how to do away with the annoying post-install setup and account setup and firewall warning. I imagine it's just a "Default User" profile adjust and deploy thing.

note: I added 30 minutes to this post for subsequent work on this topic