Last.fm: A free service that tracks your musical taste, finds similar users, and provides musical recommendations and free personalised radio.
You get your own online music profile that you can fill up with the music you like. This information is used to create a personal radio station and to find users who are similar to you. Last.fm can even play you new artists and songs you might like. It's addictive, it's growing, it's free, it's music.
Songbird, Songbordnest:
Songbird is a Web player built from Firefox's browser engine. Songbird is open source, will run on Windows, Mac OS X and Linux and supports user contributed, cross-platform extensions.
Songbird plays the Web. Play any MP3 on the Web without leaving the page. Songbird can view Web pages as dynamic playlists that it can play, save, or automatically download every day ...
The Song Tapper:
This site lets you search for a song, by tapping the rhythm of its words (lyrics). Let's say you have a song stuck in your head, and you don't know the name of it. Never fear! Load up our search screen, and try tapping the rhythm of the song on your space bar while humming the tune. Tap the space bar for each syllable that you sing. It's that simple!
After you tap the rhythm, we'll show you a list of matching songs. If we can't identify your song, you can teach our system by entering the song name.
LisenceMusic: Search LicenseMusic's online library to license pre-cleared original music for broadcast media, audio-visual, and Web productions. Our extensive music library covers nearly every musical style ...
Music-Map: Travel the world of music.
The closer two artists are, the greater the probability people will like both artists. (needs a little time to organize)