Simpler guide to get multimedia in Ubuntu

Take a terminal (Applications -> Accessories -> Terminal) and enter the following command: (You can copy and paste)

sudo wget -O /etc/apt/sources.list.d/medibuntu.list && sudo apt-get update && sudo apt-get install medibuntu-keyring && sudo apt-get update && sudo apt-get install libdvdcss2 w32codecs

The above command downloads all the required codecs from the Medibuntu repositories and makes your Ubuntu box multimedia ready.

Note: The above command is for 32 bit processors. AMD 64bit users, replace the ending word w32codecs with w64codecs. PPC users replace w32codecs with ppc-codecs.
Bonus Tip
Once you have run the above command, you can easily install third party applications like Skype, Google Earth and Acrobat Reader.

sudo apt-get install skype

Google Earth:
sudo apt-get install googleearth-4.2

Adobe Acrobat Reader:
sudo apt-get install acroread