Two popular solutions for playing MP3 files in your car or truck are to use a cassette adapter or an FM radio transmitter. These solutions may not have the greatest for the sound quality for music, but the sound quality is fine for audio books.
A short range FM transmitter wirelessly sends audio from your MP3 player to an unused FM station on your car radio. Connect the FM transmitter's short cable to your MP3 player's headphone jack. Then, use the FM transmitter's switch to select an FM frequency that has little or no interference with FM radio stations. When you plug the FM transmitter into your vehicle's cigarette lighter it will broadcast the MP3 sound to your vehicle radio on the FM frequency that you've selected.
Once you find a suitable clear FM frequency, you can leave the transmitter plugged into your cigarette lighter jack since it will be automatically powered on and off with your car's ignition. You can buy FM transmitters that are battery powered, but I don't recommend these because when the batteries weaken, they tend to broadcast poorly or not at all. Look for an FM transmitter that advertises “digital tuning” or that uses a switch or buttons to select a broadcast frequency.
M transmitters that use a dial to select the transmit frequency because they can be difficult to tune and tend to drift off station. Search at www.Froogle.com for “FM Transmitter” to find a variety of choices ranging in price from $20 to $100.
A CD/MP3/MD to cassette adapter is a cassette shell with a short cord that dangles from the mouth of your cassette player. Insert the cassette and plug the cord into your MP3 player's headphone jack to listen to your MP3 player through your car radio. You'll find a wide assortment of cassette converters at www.Froogle.com for about $6 plus shipping. You can also find cassette adapters at retail electronics stores like Best Buy.
When you eventually buy a new car, you should know that some manufacturers now offer integrated MP3 options. On the high end, some BMW's have an IPOD compatible in-dash radio that allows you to control your IPOD directly from the radio controls. Some automobiles that are targeted for the young adult market, like the Ford Focus, have in-dash compact disc players that are MP3 compatible and can play home-burned CD discs that contain MP3 files. Coincidentally, it's not widely known that most home DVD players can play your home-made CD discs that contain MP3 audio files.