The Gertboard (classic) is one of the first expansion boards for the Raspberry-Pi. It comes with an extensive manual which will lead you step-by-step through the difficulties of working with inputs and outputs: Gertboard manual. Hans-Dieter Busch has translated the document in German and has made that available to me: Gertboard Benutzerhandbuch. The code used in the manuals is also available. The C-code: Gertboard code (C) .zip   and the Python code: Gertboard code (Python) .zip. For instructions how to unpack the archives look here.  There is a forum for the Gertboard on the Raspberry-Pi website: here.
- The Gertduino