NEW YORK (CNN/Money) - They're everywhere - on the bus, at the gym. Wherever people congregate, they're listening to MP3 players. And there's a good chance each person is using a different make or model. At last count, there were well more than 100 different players out there. So picking one can be, shall we say, a challenge. But if you know what you're looking for, you'll be able to eliminate many lesser models right off the bat.

The first thing you need to know is how much music you want to put on your player. This can get a bit confusing, so pay attention. A good rule of thumb is that tunes recorded at so-called "CD quality" (128Kbps, aka the bit rate) will take about 1MB of space for each minute of music. A five minute song takes up about 5MB. The same song recorded at 192Kbps, which gives higher sound quality, will take up more than 7MB of space.

Next, you'll need to know where you want to use it. If you're just looking for a player to attach to your home stereo system, for example, you'll want one with a large hard drive that gives you the option of recording music at a higher bit rate. These players tend to be bigger than smaller, portables with less storage capacity; that's why many portables accept SD, SmartMedia, MultiMedia or CompactFlash cards as a means of storing additional music.

More tech gift guides • Great PCs for under a grand • How to buy a digital camcorder • Picking the right digital still camera

Cards are cool if you like to change the music on your machine frequently. If you have all the tunes from your "Disco Fever" period on one card and those from your "Dark Side of the Moon" period on another, you can swap them as the mood strikes you.

Finally, there's price. MP3 player prices have dropped significantly in the last few years. So you need to ask how much you want to spend? Whatever your price level, you'll find something to fit your budget.

The headphones that come with these devices vary widely. Some sound great but aren't comfortable. Others fit nicely but sound lousy. Most MP3 players come with ear buds, which I can't stand, so I know going in that I'm going to have to replace them.

Here are five players I think are worth a look.

If you're looking for big space, there's the Nomad Jukebox 3 ($500) from Creative Labs. It has an enormous 40GB hard drive, which the company claims can store 5,000 songs. For audiophiles who record at the device's highest bit rate (320Kbps) that number drops significantly. Personally, even though I don't have that much music that I really like, it's nice to know the device has the capacity to handle it if my kids want to add, say, the soundtrack from Harry Potter.

(Photo: Creative Labs)

This device has both a USB and super fast FireWire connection. If you have a lot of music on your PC and you want to transfer it quickly, FireWire is best. Like the iPod, you can use this device to store documents or other files. It also has Volume Management, so volume remains fixed from one song to the next. Another cool feature is the Environmental Effects setting that allows you to select Concert Hall or Arena sound. They say it's portable, and it is, sort of.

The Apple iPod is the gem of today's portable MP3 players and comes in three configurations for the Mac and the PC: a 5GB player that holds 1,000 songs ($299), a 10GB version, which holds 2,000 ($399) and a 20GB version that holds up to 4,000 ($499). It's small and amazingly easy to use. But the thing that sets the device apart from other players is its 32MB cache, or short-term memory, which stores 20 minutes of music. Since music is stored in the cache, the iPod isn't bothered by bumps or other movement. For a portable, that's a big deal. The iPod has 20 presets for equalization, so you can adjust the sound depending on what type of music you're listening to, whether it's jazz, rock, or classical. It even has software that allows you to store contacts and keep a calendar.

(Photo: Archos)

In the one-device-does-everything category is the Archos Jukebox Multimedia 20 ($375). This player has a large 20GB hard drive, but the most impressive thing about it is that you can display video or photos on its crisp 1.5-inch LCD screen. It connects via FireWire and USB 2, so transfers are very fast. The Multimedia 20 also has a built-in microphone and audio input that allows you to record music directly from sources other than your computer. For multimedia fanatics, the Archos Jukebox Multimedia 20 is a pretty good deal.

(Photo: Creative Labs)

It's not loaded with bells and whistles, but for a basic portable the Creative Nomad MuVo ($150) is a very good option. Like other small players, the MuVo is limited in how much music it actually holds -- in this case, it's only 128MB. On the other hand, the MuVo is a mere 2.9 inches long and 1.4 inches deep with a weight of one ounce. Yep, one single ounce. That's hard to beat. There's no display so you won't be changing settings on the player while you listen -- everything is done on your PC. And functions are limited to skip, fast forward/rewind and repeat. Just the same, if your want a player that won't weigh you down on the treadmill, the MuVo is it.

(Photo: Pogo Products)

If you want a portable MP3 player but don't want to deal with a PC, take a look at the Pogo RipFlash 128 ($180). This 128MB player allows you to plug in any external audio source and convert the material to an MP3, whether it's a CD or cassette. You don't need a PC to get the benefits of a small, portable MP3 player. And that in itself makes the Pogo worth the price.