For deployment of Skype 5.8 version  use the following link to download the msi package:

http://www.skype.com/intl/en/business/download/ 

Then use the following commandline to get it installed silently:

msiexec.exe /i skypesetup.msi /qn STARTSKYPE=FALSE SKYPEREMOVAL=DEFAULT ALLUSERS=1

Source: http://community.skype.com/t5/Windows/Unattended-install/td-p/184628