I see I have another hit this morning for search terms related to installing Skype on Scientific Linux. I followed the instructions at the CentOS wiki. From there, you can either edit the menu, add a launcher to your Gnome panel, or whatever to launch it. I chose a launcher from the panel and found a Skype icon in its installed directory (which, if you follow the instructions above, will be in /opt/skype_static-version-number/icons).
Installing Skype – Scientific Linux