USB-to-Serial Adapter
This is a USB-to-Serial adapter designed around the Texas Instruments TUSB3410.
The header connects directly to a Xilinx Spartan-3 dev board, and jumpers allow the TUSB3410 to be powered from the USB power or the dev board's 5V or 3.3V rail.
I wanted this instead of the more popular USB-to-serial dongles because the IO is logic level (3.3V) instead of +/-15V, and there's no reason to use a bulky DB-9 connector.