Songbird is an open source music player from the Mozilla stable. It is under active development and can be run on several platforms. Moreover, songbird offers several integrated services such as integrated music store, several fm and shoutcast station , concert tickets etc.
For trying out songbird you can get source/binary from the songbird website. If you are on ubuntu, ready to use packages are available at getdeb.
For installation , grab the deb corresponding to your version of ubuntu.
On my Jaunty box I did
$ sudo apt-get install songbird_1.2.0-1~getdeb1_i386.deb
Song bird appeared under Application-Sound and Video->Songbird
When I clicked on the menu item it showed me the songbird licence and proceeded to ask some configuration questions. Finally, I got the following screen and I started listening immediately,
You can do anything that you do in rhythmbox. Songbird Rocks !!