Spotify is software that allows you to listen to your favorite music via peer-to-peer streaming without waiting for the famous delays of "buffering“, simply by searching for the author or title of the song; you will no longer need to save all your music locally on your computer!
The program is available for Windows, Mac and also works with Linux via wine and has a simple and intuitive interface. The version for will also be available soon iPhone to always have all the music available when you are out and about.
The service is legal and free in some areas of Europe because it is based on advertising. Unfortunately, Spain is not included among these nations (it is possible to sign up for a premium subscription for €9,99 per month) but there is a solution for this too :)
Find out how to have a completely free account with Spotify reading a detailed guide on Kurt's blog and try it because it's really worth it.
Spotify: All the music you want for free!