iPod enthusiast Matt Gilbert has thrown together a nice, cost-efficient hack to get the iPod running directly to a car stereo without having an auxiliary input. He had experienced static and interference when using FM Transmitters or cassette adapters, and this tweak uses a toggle switch and some wire splicing to create a direct line-in into any car stereo.
The total cost of the mod is under $1 (if you already have basic wiring tools and supplies), and it’s a great way to ruin your dashboard if you mess up.
Car Stereo Auxiliary Input [MattGilbert]