Last.fm is actually an intelligent service (kinda :)) because by using information such as the ones that you're currently listening and your friends and their recommendations... it can make "suggestions" to you by trying to figure out what you like as well.
Anyhow, you can either use their web site to listen to all the radios, music (not everything is free though) etc which is not that cool because you always have to open the web browser and enter the proper URL, etc... in that case you can use graphical frontends such as Vagalume which is created for that exact purpose!.
|You have to register at "last.fm" first... (it's free)|
*. Clean and easy to use GUI written in GTK+ toolkit thus integrates well with Gnome desktop (although you can use it in other desktops nonetheless).
*. Play Last.fm radios or music tracks.
*. Add/edit radio channels.
*. Download and save tracks to HDD.
*. Create playlists, bookmark, run in the system tray (can be disabled) and will give you notifications of the currently playing song (like many other audio plyers) are the main ones to mention.
You can install the excellent Vagalume (0.8.4 current version) in Ubuntu 11.04 Natty Narwhal (may work in 10.10 and 10.04) by using the below command in your Terminal window.
sudo apt-get install vagalumeOnce installed you can launch it from: "Applications" -> "Sound and Video" -> "Vagalume". Yep... that's it. Enjoy the music dudes and dudees ;-).