What are some alternatives?
When comparing Last.fm and Serendipity by Spotify, you can also consider the following products
Pandora - Pandora Radio is a free (ad-supported) internet radio founded in 2000.
Google Play Music - Free radio for everything you do. Store 50,000 tracks from your personal collection. Subscribe for on-demand access to 40 million songs and offline listening.
SoundCloud - Enjoy music & follow favourite artists
Deezer - Deezer is a music streaming app created in France. It is available in 180 counties and gets 16 million users a month. 6 million of the users have paid subscriptions. Read more about Deezer.
TuneIn Radio - With TuneIn Radio Mobile, your mobile device becomes the radio.
iTunes - Media player, media library, Internet radio broadcaster, and iPhone device management application