Aiwa CDC-MP3
A car stereo that has been out since 2001 or 2002 which plays normal CDs, as well as CD-Rs full of MP3s.
This allows the average user to put about 9 hours of music on a 10 cent disc in 5 minutes.
A DVD-R version would be very helpful, and store about 72 hours of music, but it is unknown if Aiwa is working on such a unit.