We need to add the Medibuntu repository (Ubuntu 7.10),
sudo wget http://www.medibuntu.org/sources.list.d/gutsy.list -O /etc/apt/sources.list.d/medibuntu.list
then, add the GPG Key,
sudo apt-get update && sudo apt-get install medibuntu-keyring && sudo apt-get update
You may be asked to accept this package even though it cannot be authenticated. This is normal; typing “Yes” means you trust Medibuntu.
Finally, we install Skype,
sudo aptitude install skype