Spotify on Linux now supports all Spotify accounts, offers 15 million tracks for free accounts.
Install Spotify desktop client in Ubuntu:
This is a preview build of Spotify for Linux. .deb packges for Ubuntu user are available from repository.spotify.com/pool/non-free/s/spotify/. Download appropriate one and double click to install via Ubuntu Software Center.
If you want add the spotify repository and keep it updated, open up a terminal window and do following steps:
# 1. Add this line to your list of repositories by editing your /etc/apt/sources.list
sudo gedit /etc/apt/sources.list
deb http://repository.spotify.com stable non-free
# 2. If you want to verify the downloaded packages,
# you will need to add our public key
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 4E9CFF4E
# 3. Run apt-get update
sudo apt-get update
# 4. Install spotify!
sudo apt-get install spotify-client-qt