Check out this neat R-Pi breakout, called Step_X. Steve writes:
The Step_X (Stephen’s Experimenter) board. complete (at the moment) with some annotation to indicate major areas. The concept is to have one place to gather some simple I/O tools addressed by the Raaspberry Pi GPIO, which is further protected and buffered by zener diodes and a series of OCL darlington drivers to ‘push’ more from the GPIO. No ADC on board but easily added. You can make one as well.
You can find more pictures, videos and info in his RasPi set on Flickr.
Nice work, Steve!