GPIOs

RPi Low-level peripherals:
http://elinux.org/Rpi_Low-level_peripherals

Interrupts:
http://raspi.tv/2013/how-to-use-interrupts-with-python-on-the-raspberry-pi-and-rpi-gpio

Shutdownbutton for the paper-duino-pi, button on Pin 22 with internal pull-down resistor.
shutdownbutton.py.7z

Blinking LED