For Ubuntu 15.04 and 14.04 LTS (12.04 or later)

Run the following:

sudo apt-get install curl
curl | sudo apt-key add -
echo "deb ./" | sudo tee /etc/apt/sources.list.d/libdvdcss.list
sudo apt-get update
sudo apt-get install vlc vlc-data vlc-plugin-pulse browser-plugin-vlc mplayer2 smplayer ubuntu-restricted-extras

Enable full DVD support (depending on which Ubuntu release, these three packages may already be installed)

sudo apt-get install libdvdcss2 libdvdnav4 libdvdread4
sudo /usr/share/doc/libdvdread4/