In a comment to an earlier post, Bucky has suggested adding the medibuntu repository to ubuntu, rather than adding the skype repository to install skype. medibuntu (multimedia, entertainment & distractions in ubuntu) has the skype package, as well as many other packages that you may find useful or as the name suggests, entertaining, such as realplayer and google earth.
Before going further, you should be aware that the medibuntu repository also contains packages that are not included in vanilla ubuntu for legal reasons. medibuntu.org (which you should read before continuing) states:
It is your legal responsibility to make sure that the software you are installing can be legally used in your country and for your intended purpose.
With that in mind, to add the medibuntu repository and keyring, and update your sources to include the medibuntu packages, in a terminal:
sudo wget http://www.medibuntu.org/sources.list.d/`lsb_release -cs`.list --output-document=/etc/apt/sources.list.d/medibuntu.list; sudo apt-get -q update; sudo apt-get --yes -q --allow-unauthenticated install medibuntu-keyring; sudo apt-get -q update
If you want to see what packages you can now install, open the “Synaptic Package Manager” from the Administration menu, click the “Origin” button, and then select from the three medibuntu repositories (free, multi-verse, non-free) in the left panel.