Data Sheet.

Arduino MEGA 2560
http://arduino.cc/en/Main/ArduinoBoardMega

Arduino ETH Shield
http://arduino.cc/en/Main/ArduinoEthernetShield

PCF8574A/AP
http://www.nxp.com/documents/data_sheet/PCF8574_PCF8574A.pdf

Keyboard 4x4
http://www.mikroe.com/downloads/get/1215/

LCD 20x4
http://www.systronix.com/access/Systronix_20x4_lcd_brief_data.pdf

PCA9600
http://www.nxp.com/documents/data_sheet/PCA9600.pdf