Jabber is the only mainstream free (as in speech) instant messaging protocol. Unfortunately, most Jabber clients for GNU/Linux only provide options for messaging and group chats, overlooking the audio chatting portion of Jabber (powered by the Google-funded libjingle). Enter Jabbin, the free Qt-based Jabber VoIP client.
There was a time when geeks were the only ones who used instant messengers. Not so now. Almost everyone, from high school students to Congressmen, have instant messaging accounts. Businesses use instant messengers like Lotus Sametime or Novell GroupWise within their companies. How did instant messengers get this far?