I've put together a USB Mass Storage driver for the Maple.
https://github.com/joeferner/maple-usbMassStorage
I've been able to successfully play MP3 from an SDCard using sdfat library through the Maple.
The example in the library also adds two special files /PROC/REBOOT and /PROC/BOOTLOAD which allow you to reboot and enter the bootloader from the host PC. Just write a value to either of those files.
