XBMC is an award-winning free and open source (GPL) software media player and entertainment hub for digital media. XBMC is available for Linux, OSX, and Windows. Created in 2003 by a group of like minded programmers, XBMC is a non-profit project run and developed by volunteers located around the world. More than 50 software developers have contributed to XBMC, and 100-plus translators have worked to expand its reach, making it available in more than 30 languages.
While XBMC functions very well as a standard media player application for your computer, it has been designed to be the perfect companion for your HTPC. Supporting an almost endless range of remote controls, and combined with its beautiful interface and powerful skinning engine, XBMC feels very natural to use from the couch and is the ideal solution for your home theater.
Install XBMC on ubuntu 11.10 (Oneiric)
Open the terminal and run the following commands
sudo apt-add-repository ppa:nathan-renniewaldock/xbmc-stable
sudo apt-get update
sudo apt-get install xbmc