If you're not on board already, head over and register for a free account at Spotify and download their player now. Building on Nokia's badly presented, but solid concept of 'comes with music', the program works like iTunes, or a totally unlocked Last FM - but stores no music on your hard drive. Music is all delivered legally over the www as and when you play it, at a bitrate comparable to decent mp3 compression. A basic account is free, with the only concession being the occasional advert. And currently that is occasional - with only about 3 ads playing over 8 hours of continuos use at the moment, and most of them were for Spotify's own premium service. For that premium service you can pay 99p a day, or £9.99 a month for advert-free listening - which is hardly extortion.
The concept has come a long way since I last checked in, with the selection now being pretty thorough. Some of the usual cautious big-hitters (Beatles, Led Zep, Pink Floyd, Metallica) are absent, and a few labels are obviously not quite there yet (e.g. Sub Pop, Jagjaguwar) but on the whole the catalogue is on a simlar footing to iTunes - and they even have a few exclusives, like a one week heads-up on U2's new album.
Search for an album, press play and you're off. So easy it's ridiculous.
We're already using it heavily at Chimp HQ - particularly thanks to the built in support for Last FM, which lets us keep our charts up-to-date with minimum hassle - and I dare say this app (or at least the concept) will undoubtedly define the future of music, just as Napster, iPods and iTunes all have. You have been warned.