Just wanted to give a little free advertisement for a distributed tool we use called Sococo. It is basically a multi person voice and text chat system that overlays a virtual office on top. This allows for some organization of teams, easy switching between teams and individuals for communication. It also has multiple screen sharing, so up to 4 people can be sharing their screen at once in one single chat room.
Their is most likely current plans to make this a paid software as they add new features(Skype and file sharing on its way). So if they keep up this quality and innovation it is definitely a tool to keep an eye on.