Webpages that make you go CTRL+D: Spotify

I recently discovered this web page called Spotify. As its webpage describes it, it is a "world of music. Instant, simple and free"... it can not be described better.
It works by invitation or with a monthly fee. Once you get the invitation (or pay the €10 fee for a month), you get access to an amazing database of music, which you can listen from your computer connected to the internet. I can not say that you will find absolutely everything available in the world of music, but almost, although apparently, what you get depends on the country where you are.
Enjoy!!!