For those of us with jobs that require sitting in front of a computer, the days of listening to the radio as accompaniment may be long over. (We know there are some holdouts.) Now, we can get all the free music play we want right from our PC, over the Internet. And with the advent of those little handheld computers called smartphones, all of this free music can travel with us.

There are generally two ways to listen to free music online: a streaming music service lets you control the content and Internet radio streams either entire stations or songs based on your preferences. (Hey, it may not be your favorite song, but it has a lot of the same notes.) You can set up an account with all of them and pick what best suits your mood or the task at hand. With many services, you'll rarely need to interact; let it do its thing while you do yours—just like the FM stations of yore. You might even discover some new winners on the way.

Here's a quick look at the leading services that will get free music buzzing in your ears no matter where you go.

What Pandora lacks is playlists. You don't get to pick your lineup, only the first song the station you create is based on. Voting up or down on songs played helps steer the station to your tastes. Any downside is outweighed almost entirely by the fact that you can listen to Pandora almost everywhere; it has apps for nearly every platform or device.

Pandora lacks a lot of what Spotify has to offer, but its ubiquity and simplicity may make it all you would desire.

Mobile Apps: iPhone, iPad, Android, Blackberry, Palm Pre

Devices: Blu-ray players and home theater systesm from Sony, Panasonic, Samsung, Toshiba; TV providers like DirecTV, DISH Network, Verizon FiOS; streaming media boxes such as Boxee Box, Logitech SqueezeBox; other devices like the Chumby, HP DreamScreen, Logitech Wi-Fi Music Player and more. (See complete list.)

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Read PCMag's review of Pandora Radio (Fall 2011).

We call Spotify "a cloud-based version of iTunes," because you don't have to store music locally. You can access the 15 million songs in the Spotify library over the Internet with the software. Create all the playlists you want—or a giant playlist, since one can contain 10,000 songs. Last month, Spotify added the ability to create Pandora-esque radio stations in the program, available even for free accounts.

To avoid ads, you can pay $4.99 a month to store some music locally for offline playback. The mobile apps for iOS will store up to 3,333 tracks locally for offline play. If you pay $9.99 a month, you can listen to albums before they're out and get playback at 320kbps, a much higher quality than the free version.

You won't find it on as many devices as you can find Pandora, but Spotify could pack enough perks to make you forgo Pandora and even iTunes (if you're only into music). The price is still less than buying one CD a month, yet the music options are almost endless.

Mobile Apps: iPhone, iPad (Android is in preview) for free; Premium users can also use Windows Phone, Palms, and Symbian at m.spotify.com

Read PCMag's review of Spotify and Spotify for iPad.