I was looking at the 2009 Honda Fit the other day and was delighted to see that it has a USB port where one can plug in a usb flash drive loaded with your music library. It's a simple matter then to access the tunes on the flash drive via the built-in Honda radio/audio system. It's also cool that the USB port is located in a closed pocket so no one outside the car can see it. If an upcoming Prius gets this, I'll be in heaven.
I like the idea but I would like to see it go further. Perhaps DivX support for movies and such... possibly back seat player for the kids.