Moving along the Philips ARM Design Contest 2005 projects list there is another interesting project you may find interesting. Its a flash card audio player which plays lossless audio tracks directly from MMC flash card. Interesting thing is that player is controlled by car audio head-end unit.
The idea was to emulate a CD changer so the head-end could be adopted to communicate with player. Instead playing CD tracks player changes the tracks in subdirectories. Each subdirectory appears as different CD to head-end unit. Other commands like play, stop, next CD, next track are normally supported. Audio signal is converted do analog through external high speed stereo DAC. Signal is sent back ti head-end unit for amplification after when music reaches speakers. Nice project probably more for learning purposes rather than practical. Download files here.