If you have an iPod and you need to use it in your car without a tape adapter (someone made the switch to CD too soon!), you'll need an iTrip, the most effective FM transmitter made exclusively for the iPod. It's a little, cool looking tube that you plug in to the top of your iPod, in both the earphone jack and the little device-powering jack. After a few seconds, the device kicks on and starts playing your music through a radio station (selectable if you install the included software, but it defaults to 87.9, a very rarely used frequency). It does take some juice from your iPod to run, so it's a good idea to pick up a car-to-iPod power cord, available from Griffin and Belkin, to avoid sucking your poor little iPod dry. In addition, you can turn off the little light that lets you know the iTrip's running, which simply eats up battery power. I've tried several FM transmitters, and this one seems to work the best; in my testing, there were a few normal pops and some static, but far less than Belkin's comparable products, which cost about the same.