Amarok is a powerful music player with an intuitive interface. It makes playing the music you love and discovering new music easier than ever before and it looks good doing it! Amarok is based on the powerful Qt4 / KDE4 Platform and nicely integrates with KDE desktop.

Much work has been invested into integrating Amarok 2 with various Web services:

Ampache
Jamendo Service
Last.fm
Librivox
MP3tunes
Magnatune
OPML Podcast Directory

Amarok comes with a lot of features including but not limited to:

Scripts – enhance your Amarok experience with community developed scripts.
Dynamic Playlists – create playlists that automatically update.
Context View – customize interface with the Plasma powered Context View.
PopUp Dropper – simplify drag&drop actions with revolutionary menu system.
Multiple Language Translations
Collection Management – organizing your music collection has never been easier with Amarok’s powerful tagging, renaming, and sorting abilities.
Database Importing – import collections from Amarok 1.4 or iTunes.
Scriptable Services – integrate other web services into Amarok.

Amarok is default available in Ubuntu Software Center, but it might be old. To get the latest version, you can add Kubuntu-ppa and install with following commands:

sudo add-apt-repository ppa:kubuntu-ppa/backports
sudo apt-get update
sudo apt-get  install amarok

And finally find it under Applications -> Sound & Video.