Tong Family Blog: Perfect in car adapter. So I got this adapter for our cars and I have to say although you get it from Apple, so it is expensive, it is really the perfect adapter. The only trick is that there is a tiny switch at the bottom which you set to low volume for today's iPod, otherwise, it amplifies too much and sounds distorted.
There are some other good resources and quite a few solutions at "DigitalMania-Online":http://www.digitalmania-online.com/iPod-Auto-Accessories.html so for instance there is "MP3YourCar":http://www.mp3yourcar.com/ which offers you direct connection to the CD input. This does require an installation though.