Ekiga is a shiny new VoIP-application. The successor of old gnomemeeting featuring SIP-Support and much more. The name has been changed for a reason: to show that it is not only for gnome. And as you can see on the screenshot I am using kde with ekiga and it works perfectly.
It is one of the best open source VoIP applications out there, although in my opinion skype has still the better audio quality. But if you want to use open standards like SIP or H323 then ekiga is for you. You can also try another voip client application for linux, some are not in portage yet:
As ekiga is included in gnome-2.14 it was originally masked but I unmasked it today because it does not depend on any other gnome-2.14 components. Please test it and help me to make the ebuild as good as possible.