Kindly Note: Do this at your own risk, Chances are that, you could spoil you Ipod and your Car Audio.
How you can make your car Audio, Ipod Enabled, I have a Pioneer Car Audio and Ipod Mini. You need Audio cables and stereo 2 mono pin.

Step 1: Check Whether Your Car Audio Has AUX

Before you start this experiment check whether you Audio system support AUX, I have a Pioneer CD Player which supports AUX

Step 2: Remove Your Car Audio From Your Car.

After you remove your car Audio examine at the back to find left and the right channels

Step 3: Stereo 2 Mono Out Pin

What you see is a Stereo 2 mono out pin which is very much required for you to connect your Ipod Output.

Step 4: Audio Cables

What you see is the Audio Video cable Which I had a spare, you can use just the Audio cables instead of 3 wires you will have only 2 pins on eigther sides

Step 5: Connect Your Stereo 2 Mono Pin

Use one end of your Audio cable to connect with stereo 2 mono pin

Step 6: Connect Your Audio Cable

Use the other end of the Audio cable to connect to your car Audio System

Step 7: Connect Your Ipod

Now choose the Stereo 2 mono pin and connect it to your Ipod output

Step 8: Now Take a Test Drive

Put your car audio back in to the same position of your car and I hope you remember the power connections and other cable connections.

Choose the Tuner/Radio, play the ipod and you should be able to hear the music/podcast.

After I bought the Ipod I have thinking of hearing the podcast while I travel in my Car, I travel around 22 KMS which actually takes me an hour on Indian roads during peak hours.

Disclaimer: Try it at your OWN RISK, I am not responsible for any damages for any of your belongings, I have tried and it works for me.