I've posted an article on a very simple way to install a direct car audio connection for an iPod in place of an existing CD changer. My pal Kevin C. was the first to try this concept and it works great.

It's a good alternative to using an FM transmitter or a cassette adapter. And since you wouldn't want to use your CD changer anyway once you have this set up, it's perfect to steal the CD changer's audio connection for it.

If you opt for an FM transmitter, the Griffin iTrip has been around for a while, but the newly released Monster iCarPlay is a more complete solution because it provides power (no battery drain) and also charges the iPod.