MP3 players come in all shapes and sizes, but they share one common trait — good as they are right out of the box, a little accessorizing just makes them better.

Your MP3 player's already a great portable jukebox — that's its main function. You might have a player that also lets you watch downloaded TV shows or movies. But what about using your player as a video source for your home theater or as a music source for your car stereo? All you need are the right accessories.

First things first: protect your MP3 player

This Belkin leather sleeve protects an iPod nano while allowing full access to controls.

Portable listening is the core use of just about every MP3 player, regardless of its size. It's a good idea to protect your player with some kind of case as you go out and about. There are a variety of cases available — some made for specific models, others compatible with many different kinds of players. Most feature a clear panel to shield the player's screen, and some include padding or a folding flap for even more protection.

If you like to listen on walks or workouts, you can find a case outfitted for easy mobility with an attached arm band, belt clip, neck strap, or wrist strap. Some cases even have built-in speakers for places where you don't have to keep your music to yourself. And you don't have to sacrifice style for functionality. Cases come in a variety of colors and designs, from conservative black leather to neon pink, blue, and green.

Want a "case" that can hold your books, keys, and cell phone in addition to your MP3 player? Check out the backpacks. They come in different colors, have a special pouch for holding your player, and storage aplenty for your books, laptop, and just about anything else you need to take with you.

Listening options on-the-go and at home

Possibilities abound for listening to your MP3 player on the go. One of the first accessories many people pick up is a nice set of headphones. The quality of headphones ranges widely, from affordable "sport" designs to noise-canceling models with impressive bass and clarity. You may also want to consider a Y-adapter, which lets you plug two sets of headphones into one player. This can be helpful for listening on an airplane, train, bus, or any other setting where you want to share your music with one other person.

At home, you can choose from a wide array of speaker possibilities. There are mono, stereo, and even 2.1-channel speaker systems designed for getting fuller sound from an MP3 player. And don't rule out your current audio/video system. A minijack-to-full-size RCA cable lets you run a line from your player's headphone jack to your receiver's auxiliary input, letting you play your stored music through your system's speakers.

Here's a sample of what's available:

The speakers on the iLive iS108B fold flat for portability.

• Personal speaker systems — Your MP3 player usually connects to these systems through a stereo minijack cable. Just plug your player in, and enjoy the sound. Many of these systems are also portable, so you can take them to a friend's house, the basketball court, or anywhere you want to listen. These typically run on batteries (usually "AA"s) or AC power.
• Computer speakers — Some speaker systems designed to provide multichannel sound from your computer can also work with your MP3 player. These systems connect to your player quickly and easily via a stereo minijack cable. And since many include subwoofers, they can deliver even more room-filling sound than portable systems.

And there are wireless solutions for listening to your MP3 player at home. Employing RF, Wi-Fi® or Bluetooth® technology, wireless transmitters plug into your player's headphone jack and transfer data across your living room to a receiver connected to your audio/video system or powered speakers. Some even let you add additional receivers.

Listening in the car

What's the best way to listen to your MP3 player while you drive? Well, it depends on your car's stereo, your budget, and the level of convenience and sound quality you want. You can choose a basic, inexpensive solution, or a high-end option that delivers optimal sound quality and lets you control your player using your car's radio.

Use the digital drive-thru® tool at crutchfield.com to find an adapter for your specific MP3 player, vehicle, and stereo system.

Whatever option you choose, make sure you have an accessory that lets you secure your MP3 player in the car. Whether it's a universal mount that attaches to the car's interior, or a vehicle-specific mount that bolts onto the dash, one of these simple gadgets can keep your player from flying around your car at a sudden stop.

Now, let's take a look at what's available for getting music from your MP3 player to your car's radio.

Budget-friendly accessories

• Cassette adapter — This gadget has been around for a while, and it's still as easy to use as ever. Just plug it into your player's headphone jack, and place the adapter in your cassette player. The resulting sound quality is on par with a standard cassette tape.
• Wireless FM transmitter — Like the cassette adapter, this device plugs into the player's headphone jack. But instead of using your car's cassette deck, it turns the music from your iPod into an FM signal, which it transmits to your car's radio. These devices can be powered by "AAA" batteries or your car's cigarette lighter. This option is simple and easy to install, but in some locations, interference and static can be a problem.

Getting better sound quality in your car

• Wired FM modulator — Much like a wireless FM transmitter, this device sends a signal to your car's FM radio. But unlike the wireless solution, the wired FM modulator transmits directly to the radio's antenna input, so the signal is much stronger. The FM modulator is still susceptible to interference from surrounding stations, however.
• Car receiver — Some car receivers — also known as head units — are equipped with an auxiliary input jack, which allows you to connect your iPod directly to your car's radio using a minijack-to-RCA cable. While some head units have an aux input conveniently located on the front panel, many place the aux input in back, requiring you to run the cable under the dash.
• Bluetooth adapter — If you want to connect your player to your car's radio wirelessly, consider the Bluetooth options. These newer adapters consist of a transmitter, which plugs into the player's headphone jack, and a receiver, which plugs into your head unit's auxiliary input. Sound quality is just as good as a wired connection, but without wires running to and from your dash.