There are mainly two kinds of music download services online. There's the services that allow you to buy tracks you can download and then there are subscription services that let you listen to full tracks online in return for a monthly subscription fee. Some do both.

Introducing http://Walmart.com

Pretty straight forward service that lets you purchase tracks to download. Last time I checked, they were offering music downloads for 88 cents per download and let you choose from over 800,000 songs in their catalog. They also have a service where they let you choose up to 20 tracks from about 500,000 songs, burn them to CD and then ship you the CD.

They are the only service in the four mentioned in this article that allow you to view and purchase music from their catalog without having to download some kind of player to your local computer. All you need is Internet Explorer.

Itunes.com, the granddad of revolution

Owned by Apple, Itunes was responsible for really kicking off the music download service industry in a big way. They were the first ones to offer the ability to legitimately pay only 99 cents for a track.

Their music catalog includes over 2,000,000+ songs, more than any other service, over 3000+ music videos, tv shows, 20,000+ podcasts, 16,000+ audiobooks and more. As you can see, they are more than simply a music store but instead offer a whole range of multimedia downloads and options.

One small drawback to their service is that you have to download and install their player which at last count was over 34MB in size before you can use their service. http://Walmart.com in contrast allows you to browse and purchase music entirely from within Internet Explorer.

Napster from pirate to megastar

Napster offers you unlimited access to 1,500,000+ songs.You can listen to an unlimited amount of music each month. You get over 50 commercial free and interactive radio stations. You can discover what other people are listening to with easy to use sharing features allowing you to swap songs with other Napster members.

Napster also allows you to burn the tracks you buy to CD and listen to them wherever you go. Napster offers a 7 day free trial of their subscription service.

Rhapsody, Real's music juggernaut

Rhapsody is a service that is owned by Real. With Rhapsody you get unlimited access to over 1,500,000+songs, complete music jukebox software to manage your entire collection, and over 80 ad-free radio stations. They also allow you to create and share your playlists (a standard feature among most online music services.) You can even watch music videos and see pictures of the artists from your favorite band.

Rhapsody includes a free 14-day trial of Rhapsody Unlimited. If you don't own a credit card, they have a service they call Rhapsody - FREE where you can listen to hours of free music every month. Besides these subscription type services, you can also purchase music downloads from their RealPlayer Music Store. They have over 1,000,000 songs that are ready for purchase.

So which service is right for you? I would suggest you give each of them a try. All of them let you listen to short clips of the music before buying and the subscription services have free trials. You can't lose.