Apple iTunes | http://www.apple.com/itunes/

US, Canada, Europe, Japan, UK, Australia...

Downloadable program for Mac and Windows.

MP3tunes | http://www.mp3tunes.com/

Online music store that allows purchase of regular MP3 files, for maximum compatibility with all computers and players.

MSN Music | http://music.msn.com/

Microsoft's music store is integrated into Windows Media Player, so people who use Windows Media Player can purchase music from their desktop.

MusicNet | http://www.musicnet.com/

AOL's bundled service, right now for AOL members on Windows only. Also provides music for Yahoo! Music, FYE, Tower and Virgin's download services.

Napster | http://www.napster.com/

Downloadable program for Windows. Now legal and paying.

Rhapsody | http://www.rhapsody.com/

Downloadable program for Windows, based more towards playing/streaming/listening than downloading. Rhapsody is owned by Real Networks.

Other services in alphabetical order:

Arvato | http://www.arvato.com/

German-based website that offers a la carte downloads and focuses on both independent and major label music.

AudioLunchbox | http://www.audiolunchbox.com/

One of the first all-independent music download sites.

Bitmunk | http://bitmunk.com/

A digital marketplace.

BuyMusic | http://www.buymusic.com/

A la carte downloads for anyone with Windows IE browser.

Emusic | http://www.emusic.com/

Website for Mac, Windows, Linux where members can download up to 40 tracks per month of high-quality MP3 files.

Etherstream | http://www.etherstream.com/

Website that offers a la carte downloads.

Liquid Digital Media | http://www.walmart.com/music_downloads/introToServices.do

Liquid exclusively provides music for Wal-Mart's digital download store.

MusicIsHere | http://musicishere.com/

Site that offers a la carte downloads - based in the Latvia.

MusicMatch | http://www.musicmatch.com/download/music_intro.htm

Audio jukebox program for Windows.

MusicNow | http://www.musicnow.com/

Website that offers a la carte downloads.

NetMusic | http://www.netmusic.com/

Digital download and streaming service.

PassAlong | http://www.passalong.com/

Website that rewards participation by allowing users to "pass music along" to friends via IM or email and earn free music for helping the bands they like sell downloads.

PlayIndies | http://www.playindies.com/

Company that offers many services to independent musicians, including a site that offers a la carte downloads and focuses on independent music.

QTRnote | http://www.qtrnote.com/

Website that offers a la carte downloads.

Ruckus | http://www.ruckusnetwork.com/

Ruckus is a subscription download service designed exclusively for colleges and universities. Participating schools pay a monthly subscription fee to provide their students with all-you-can-eat "tethered" downloads.

Sony Connect | http://www.sonyconnect.com

Sony's digital download store.

TreeTunes | http://www.treetunes.com/store/

Website that offers a la carte downloads and focuses on independent music.

WrapFactory | http://mediaforge.com/wrapfactory-music.aspx

WrapFactory distributes music as "wraps" - protected files that include photos and customizable artist info with the audio.