Jami
Jami (formerly GNU Ring) is a peer-to-peer communication solution, offering voice, video and chat in a decentralised and secure way. It is being developed by Savoir-faire Linux, a Canadian company specialising in free software.
The ancestor of Jami is SFLphone, a portable SIP/AIX software phone, also developed by Savoir-faire Linux. Jami retains most of the audio and SIP capabilities of SFLphone, while adding a Bittorrent-like DHT to completely avoid dependency on servers, and offering video and chat communication.
Additionally, Jami has a clean separation between daemon and user interface. The supported platforms are GNU/Linux, Windows, Mac OSX and Android.
Installation
Install either jami-qt for the Qt client or jami-gnome for the GTK.
Usage
$ jami
The above command will detect which client is installed (GNOME or Qt) and run it. The daemon will be launched automatically by the client.