Lots of different ways getting listed here, many using an FM transmitter. I do that for rental cars, but have quite a different set-up for my own car. BTW the Belkin TuneCast II is now under $20 all over the place, Walmart for example:
http://www.walmart.com/catalog/produ...uct_id=2603620
I found a multi-media 4.1 surround system, with the typical power supply that you plug into your home 110-120 volt AC outlet for it's input, and (this is important) 12 volts DC for it's output. It was easy to simply replace that wall plugin unit for a cable with cigarette lighter plug at one end, and the same little terminal connector plug at the other end as what the original power supply had. So, my music goes directly out of Touch and into a multimedia sound system. The hardest part was finding places behind the dash and rear side pannels where I could mount the little satellite speakers. The bigger turbo subwoffer sort of cramps foot space for anybody sitting directly behind driver's seat. Oh well, the sound is more important, and it really is great!