If you don't want to spend a lot of money, and only have a stock unit with no aux input, your best bet is an in-line FM transmitter. It plugs directly into the back of the stereo and then the antenna goes into the transmitter. It essentially "kills" your antenna when you turn it on, so you can't get any interference. You'll still only get FM-quality stereo sound, but it's the best FM-quality stereo sound that you can get on a stock unit. I have a Dension IceLink adapter (it uses the dock on the iPod), it cost about $130 at the time I got it (about 3 years ago), it is basically a CD-Changer emulator, so you get the absolute best sound possible from your iPod. In my wife's car we bought a Pioneer unit that came with a free iPod cable, which also uses the dock. Again, an in-line FM transmitter is your cheapest "good sound" solution. They're very easy to install (pull out the stereo, plug in the antenna adapter, and steal a ground and +12 connection and you're good to go).