Installing Skype under Xunbutu is not hard, but if you are having problems while installing, there is a good chance that you either might have the wrong version (32 or 64 bits) or you are not able to download additional packages because you don’t have the source set (yours trully).
If this is your case, then the solution is simple: Using the terminal, add the source and update it, so you have all sources set. Since this will vary by version, check this post on the Mediabuntu Community under adding repositories.
Run both commands and downlaod the Skype package from the Skype Linux Download Page.
Run the package installer and you should be good to go.
Have fun [Linux Version]