2.0 Alphabet

is for Last.fm, which "taps the wisdom of the crowds, leveraging each user's musical profile to make personalised recommendations, connect users who share similar tastes, provide custom radio streams, and much more." Listen online. Yes, it's very cool; CBS liked it so much that it bought the site last May.

Last.fm is a UK-based internet radio and music community website, founded in 2002. It claims over 21 million active users based in more than 200 countries.[1] On 30 May 2007, CBS Interactive acquired Last.fm for £140m (US$280m).
Using a music recommendation system known as "Audioscrobbler," Last.fm builds a detailed profile of each user's musical taste by recording details of all the songs the user listens to, either on the streamed radio stations or on the user's computer or portable music device. This information is transferred to Last.fm's database ("scrobbled") via a plugin installed into the user's music player. The profile data is displayed on a personal web page. The site offers numerous social networking features and can recommend and play artists similar to the user's favourites.

Users can create custom radio stations and playlists from any of the audio tracks in Last.fm's music library, and are able to listen to some individual tracks on demand, or download tracks if the rightsholder has previously authorised it. Registration is required to acquire a profile but is not necessary to view any part of the site or to listen to radio stations. [Wikipedia]