IRock wireless audio adapter
This will plug into your PDA, MP3 Player or anything with a mini plug. It transmits the audio via 4 preset radio frequencies to your car stereo. I used it with my Ipaq to play MP3s in my car. Just plug it into your MP3 player and set your radio to 88.9 (or one of the other 3 frequencies) and enjoy. I paid $30 for it a few months ago. I'll sell it for $15 shipped.