USB flash drive test bed needed.

I need a test bed to finish development of software for access to USB flash drives.

I need an Arduino USB host that supports mass storage. I have the Circuits@Home USB shield but I am interested in other options.

I have written a new generic FAT filesystem base that just requires a driver capable of reading and writing blocks. I plan to use this for USB devices and microcontrollers with 4-bit SDIO interfaces for SD cards. The filesystem base is independent of Arduino so I can also use it on standalone RTOS systems.

I am interested in USB host software for Due or Teensy that would allow mass storage support. Any pointers would be appreciated.