Portable Music Storage for Your Car?

Randy J. Parker asks: "Why don't cars provide input jacks for devices like MP3 players? My car has spectacular audio quality, but forces me to feed it with a handful of CDs. Unless you have a 'CD Text' supporting CD player and a fairly recent CD from the right company, once the CDs disappear into the changer, they become anonymous numbers: 'Disk 1', 'Disk 2', and so on. Devices like the iPod solve the problem of locating and feeding music, but can't be hitched to the car. Is there an after-market solution that doesn't sacrifice as much fidelity as a crappy cassette emulator or FM near-casting? Are there some cars with input jacks? What mechanisms are available to lobby for audio input jacks? Car manufacturers could even sell detachable storage as part of the car, at a huge margin, just like they do with radios and CD changers. This enables customers to finance the purchase of the portable storage device along with the car, opening up another demographic segment of buyers. I don't really want permanent music storage built into the car, since that would just be another device to synchronize. Ideally, I'd just carry my device, and attach it to speakers at my house, my friend's house, or the car I'm in."