Empathy is the default messaging program in Ubuntu since version 9.10. It supports text, voice, and video chat and file transfers over many different protocols. You can tell it about your accounts on all those services and do all your chatting within one application.

First open terminal(Applications/Accessories/Terminal), add the public key from the developers:

sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com FA3A1271

Then,edit /etc/apt/source.list:

sudo gedit /etc/apt/sources.list

add following into the file:
* For Jaunty (9.04) users:

 deb http://ppa.launchpad.net/telepathy/ppa/ubuntu jaunty main
    deb-src http://ppa.launchpad.net/telepathy/ppa/ubuntu jaunty main

* For Intrepid (8.10) users:

    deb http://ppa.launchpad.net/telepathy/ppa/ubuntu intrepid main
    deb-src http://ppa.launchpad.net/telepathy/ppa/ubuntu intrepid main


* For Hardy(8.04) users:

  deb http://ppa.launchpad.net/telepathy/ppa/ubuntu hardy main
    deb-src http://ppa.launchpad.net/telepathy/ppa/ubuntu hardy main

Update and install:

sudo apt-get update
sudo apt-get install empathy

Optionally, you can add more functionality/integration with the following packages:

* SIP: telepathy-sofiasip
* MSN Live / Messenger: telepathy-butterfly
* IRC: telepathy-idle
* Empathy applet: empathy-megaphone-applet
* Voice & video: libtelepathy-farsight0 python-tpfarsight
* Other: galago-eds-feed python-galago python-galago-gtk
For more information about Empathy,see:http://live.gnome.org/Empathy/Install