Sflphone is a sip/iax2 compatible softphone for linux. the sflphone project's goal is to create a robust enterprise-class desktop phone. while it can serve home users very well, it is designed with a hundred-calls-a-day receptionist in mind.
it features a flexible client/server architecture where the gtk+ client talks to the daemon through dbus and is capable of handling multiple voip connections at once.
this is the graphical client for gnome.