Future Technology Devices International Limited's $35 VF2F2 module (see figure) is a reference design utilizing the company's Vinculum VNC1L embedded USB host controller. It can transfer files between a pair of USB disks. The commercial-off-the-shelf (COTS) component is usable as is. Or, download the complete design and roll your own. The 8-bit VNC1L has 64 kbytes of flash and 4 kbytes of internal SRAM plus a pair of DMA channels.