The USB Bit Whacker is a spectacular little development board featuring the PIC18F2553. Based on the work of Brian Schmalz, the UBW is a small board with a command interpreter for basic input and output control. When attached to a Windows/Max OS X/Linux computer, the UBW will show up as an RS232 Com port! You control the individual I/O pins on the PIC through simple serial commands.
This is the sparkfun version, you can get the hardware and firmware from https://github.com/sparkfun/USB_Bit_Whacker-18F2553, I encourage you to look at the files inside as there are schematics for Eagle and board layouts as well
I like looking at the schematics for projects like this to try and inspire ideas of my own, its certainly a nice little board