The USB Bit Whacker is a hardware module based on a Microchip PIC18 that allows you to easily control I/O pins on the board using serial commands through the USB port.

Their home page is here: http://www.schmalzhaus.com/UBW/index.html

http://www.sparkfun.com/commerce/product_info.php?products_id=762

This project uses the UBW library which can be found here UBW I/O C# Library