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

raspberrypi/Raspberry PiでIO制御
http://www.pwv.co.jp/~take/TakeWiki/index.php?raspberrypi%2FRaspberry%20Pi%E3%81%A7IO%E5%88%B6%E5%BE%A1

GPIO Examples→Tux Crossing→1: A single LED
https://projects.drogon.net/raspberry-pi/gpio-examples/tux-crossing/gpio-examples-1-a-single-led/

MCP230xx GPIO Expander on the Raspberry Pi
http://learn.adafruit.com/mcp230xx-gpio-expander-on-the-raspberry-pi/overview

Raspberry Pi GPIO入出力のサンプル（Python, C言語, shellスクリプト）
http://netlog.jpn.org/r271-635/2013/01/raspberry_pi_gpio_test.html

Raspberry Pi用GPIOリボンケーブル
http://www.amazon.co.jp/ADA-862-Raspberry-Pi%E7%94%A8GPIO%E3%83%AA%E3%83%9C%E3%83%B3%E3%82%B1%E3%83%BC%E3%83%96%E3%83%AB/dp/B00BLZ5JLI

How to use GPIOs on raspberry pi (Simple I/O, PWM and UART)
https://sites.google.com/site/semilleroadt/raspberry-pi-tutorials/gpio

How to use interrupts with Python on the Raspberry Pi and RPi.GPIO
http://raspi.tv/tag/python-raspberry-pi-gpio-interrupts

WebIOPi is a fully integrated Internet of Things framework for the Raspberry Pi.
http://code.google.com/p/webiopi/

Getting Started with Raspberry Pi GPIO and Python
http://openmicros.org/index.php/articles/94-ciseco-product-documentation/raspberry-pi/217-getting-started-with-raspberry-pi-gpio-and-python

Top 10 Things to Connect to Your Raspberry Pi
http://www.raspberrypi-spy.co.uk/2013/03/top-10-things-to-connect-to-your-raspberry-pi/

RPi.GPIO 0.5.2a
https://pypi.python.org/pypi/RPi.GPIO