On a recent trip to Chicago, I used my Zaurus as a juke box. I've been using the Zaurus for short rides for a while. It's worked great for two hour bike rides and much shorter local commuting. The essential components can fit into your shirt pocket or any center console box. The long ride took a little extra equipment but a little more money and planning would make things much easier. The variety beat out multiplayer CDs and a working set up can be had for much less money.
Equipment list:
Not having to mess with CDs for the 14 hour drive was a real blessing. I'd play four hours of music and then, with my wife's help, get four more randomly selected from the lively half of my entire music collection.
The FM transmitter worked very well. There are several models at CompUSA. I got the cheap Seal model with batteries and a 12V adaptor because of it's pocket comfortable shape and battery operation. It had problems with stereo, despite claiming "full stereo sound" and I'm going to take it back to see if another one works better. For all that, the mono sound was clear in very crowded radio space. Occasionally, I'd have to switch stations due to the omnipresent and redundant NPR broadcasts would interfere. I looked around for ways to directly plug into my Honda Accord's stock radio, but it looked like a huge hassle complete with a $100 plug that might not have even fit.
More CF cards and a working random play script for the Zaurus would make things much better on the long drive. My script does not work on Zaurus, so I modified it to copy random songs to the CF. ogg123 does something strange with it's queuing when given a list that eats memory, and about 256 MB of songs will choke the Zaurus before it finishes. I ended up playing files by first letter and will eventually make some better scripts that are Zaurus specific. With better scripts, and more CF cards there would be no need for the laptop.