Skype is not available in the default configured repositories of Ubuntu so an alternate is downloading a deb package from skype and installing it but as i am an apt-get fan i would recommend adding the repositories listed below and then using

# sudo apt-get install skype

But you need to Add a Repository using the commands below before using apt-get if there is no command listed for your distro goto Medibuntu

• Ubuntu 9.04 "Jaunty Jackalope"

wget http://www.medibuntu.org/sources.list.d/jaunty.list --output-document=/etc/apt/sources.list.d/medibuntu.list

• Ubuntu 8.10 "Intrepid Ibex"

sudo wget http://www.medibuntu.org/sources.list.d/intrepid.list --output-document=/etc/apt/sources.list.d medibuntu.list