Skype is the most well known VoIP (voice over IP) client available. The protocol used by Skype is proprietary, but a binary-only Linux client is available for download. If you are feeling adventurous and want all the features you can get your hands on, try the beta version. Beta or not, select the RPM version for SUSE 9 and later.
Installing Skype is straight-forward – just follow the guidance on the download page.
Before starting Skype, make sure your soundcard is configured properly. Usually the initial installation will have taken care of this. Check that you can play media files using your audio player. Obviously, with Skype you also need a microphone to talk the person at the other end, so you should also check that the microphone works. In my setup, the microphone was turned off by default. To enable it, open the volume control from the tray icon (alternatively via the menu Applications > Multimedia > Volume Control). Switch to the “Capture” tab and ensure the microphone volume is turned up and the little microphone icon is not overlayed with a red cross.
You should now be all set to make VoIP calls.