Amazon MP3
http://www.amazonmp3.com/
Amazon's online MP3 sales service. Lets users purchase and download MP3s like anything else on Amazon's service.

Amie Street
http://amiestreet.com/
Music marketplace where songs start out free then rise in price by popularity. The reverse of most of today's fixed price music services.

BlogTalkRadio
http://www.blogtalkradio.com/
A platform for broadcasting users' own talk radio shows over the Web. Includes controls for handling callers and queuing up pre-recorded content.

CDBaby
http://www.cdbaby.com
An online music store for independent artists. Provides direct distribution for unsigned artists.

Emusic
http://emusic.com
Subscription-based and a la carte music seller. Also sells audiobooks and music from independent artists.

Finetune
http://www.finetune.com/
Music discovery and recommendation service. Also provides curated playlists and links to purchase individual tracks.

FlyTunes
http://FlyTunes.fm/
Free Web radio for your computer and mobile devices. Has both a mobile app and a desktop player.

Grooveshark
http://grooveshark.com/
Free Web-based music player lets you search and listen to tracks in your browser. You can also create and share your playlists with others.

iLike
http://www.ilike.com/
Social music sharing and discovery service. Analyzes your listening habits and gives you recommendations.

iMeem
http://www.imeem.com
Media sharing site focused on music. Users can create and share playlists and track what their friends are up to in a central feed.

iTunes
http://www.apple.com/itunes/whatis/
Apple's iTunes media store sells and recommends music. Users can also create and share mixes they've created from any content that's sold on the store.

Jamendo
http://www.jamendo.com/
Free music tracks from artists who have granted an open license on their work. Also lets you create and share playlists.

JamLegend
http://www.jamlegend.com/
JamLegend turns your keyboard and browser into a video game. You compete Guitar Hero-style against yourself or with others, using your keyboard's function keys like guitar chords.

Jango
http://www.jango.com/
Free internet radio and music recommendation tool. You drop in the name of the artist you like and it creates a station around it.

Lala
http://www.lala.com/
LaLa is a music search and discovery tool. Listen to full tracks and buy them without DRM.

Last.fm
http://www.last.fm/
Social music discovery and listening tool. Listen to full tracks, and create stations around artists you like.

Live365
http://www.live365.com
A network of Internet radio providers. Live365 serves as both a directory and a distribution channel for people who want to create their own stations.

Midomi
http://www.midomi.com
A music search that lets you look for music tracks by keyword, or by singing the song into your computer's microphone. Can also pick up a track with a 10-second clip from any audio source.

MOG
http://www.mog.com
An online encyclopedia for music. Also provides full-length tracks for all songs (through Rhapsody) and videos.

Napster
http://www.napster.com
Online music downloads and subscription service. Lets users stream and re-download purchased tracks from the Web.

Nexus Radio
http://www.nexusradio.com/
A desktop app that taps into Internet radio streams. Also lets users record online streams for offline listening.

Pandora
http://www.pandora.com/
A free music streaming and recommendation service. Changes what you're listening to based on how you vote on the track that's playing.

Project Playlist
http://www.playlist.com/
A music playlist sharing community. Lets you listen to full length tracks and build playlists that can be shared with friends.

Sellaband
http://www.sellaband.com/
Lets users invest in upcoming bands in return for the album they create using that money. Essentially a crowd-sourced record label.

Shazam
http://www.shazam.com/
Music identification service. You hold up your phone to the music that's playing and Shazam identifies the track for you.

Shoutcast
http://www.shoutcast.com/
A directory of Internet radio stations. Also lets users create their own stations which can be broadcast to the world.

SimplifyMedia
http://www.simplifymedia.com/
SimplifyMedia lets you stream your music collection to yourself, or to your friends. Works on desktop computers and mobile devices.

Slacker
http://slacker.com
An Internet radio service that provides customizable radio stations that can be accessed in the browser and on mobile devices.

Songza
http://www.songza.com/
A search engine for music tracks that lets you play them right from the results. Also doubles as a jukebox with playlists.

SpotDJ
http://www.spotdj.com/
SpotDJ is a service that analyzes your playlists and inserts segments from real DJs about the music you're listening to.