At medibuntu they offer a repository with two important codecs required to play most media and DVD files. The W32Codes is for 32 bit Linux systems, and the W64Codecs is for 64 bit systems. Libdvdcss2 is for DVD playback. Simply add the proper repository to your /etc/apt/sources.list file, also add the gpg key, hit a quick sudo apt-get update, and your ready to install your much sought after media codecs.

For Feisty run the following in a command window:

sudo wget http://www.medibuntu.org/sources.list.d/feisty.list -O /etc/apt/sources.list.d/medibuntu.list

For Gutsy Gibbon run in a command window:

sudo wget http://www.medibuntu.org/sources.list.d/gutsy.list -O /etc/apt/sources.list.d/medibuntu.list

Then add the gpg key with the following command:

wget -q http://packages.medibuntu.org/medibuntu-key.gpg -O- | sudo apt-key add - && sudo apt-get update

 Note that this command will also update your apt system, then all you have to do is install the codecs:

sudo apt-get install w32codecs libdvdcss2 or: sudo apt-get install w64codecs libdvdcss2