What do you do if you want to listen to your MP3 player in the car but your car stereo doesn t have a tape deck or line input? You certainly don t pop on your headphones (that s illegal), and affixing a set of portable speakers to your dash is a little clunky. Plus, not many get loud enough to provide decent sound over the rumble of your car. Luckily, there s another solution. As long as you have a working FM radio, you can use an FM transmitter to listen to your MP3 player over your car stereo. In fact, a couple of these devices will even work over your home stereo, though this should be done only in a pinch, as FM transmitters generally provide fairly poor sound quality. If you must use one, however, here are one pick or our recommendations for you to try.