I had a Volkswagen Beetle, and an iPod, and I wanted to have the best connection to my audio system. After a little research,and some soldering, I added a switchable rca input to the stock stereo.

I have an iPod, and a new beetle. I was tired of using the tape adapters, because they were noisy, and the tape deck tries to fast forward any time there was a bit of silence. as you all probably know, this feature cannot be turned off.
So, I went looking for another solution. the only one I could find cost way too much, and I wouldnt be able to use my cd changer.
Armed with my bentley manual, I decided to see if I could roll my own solution. And after a bit of tinkering I figured out a solution. I then ran some wire, and made some holes, and I came up with a set of rca inputs that go directly into the stereo, and if I want to listen to the cd changer, all I have to do is flick a switch.
I made these directions so others can make do this hack. However, I am not responsible for anything that happens to you, your car, or anything else that may happen. For example, when I was trying to figure out how to wire everything, my head unit made a popping noise and started to smoke, it was only a fuse, but I thought I fried my HU.
There are also some caveats, the main one being that you need to already have a CD changer. All this hack does is intercept the audio coming from the changer, it doesnt pretend to be a changer, so I doubt it will work without one. You also need to have a cd and the magazine in the changer in order to hear audio. And one final problem, whenever the disc changes (if you have more than one in the magazine) the speakers mute. So, in order prevent the stereo from muting, I just put one cd in the magazine, and it will not mute the speakers.
Now that you read through my ramblings, below is a link to the instructions.
VW Switchable Aux Input Instructions