Arduino and LED arrays: a display driven from the Internet

I finally decided to document this project initiated in 2011 while I was in expatriation in the USA. The idea was to make a connected “work” on which my friends could post the message of their choice. In the end, the result is nothing like a “work”, but hidden for example in a fir tree to make a connected Christmas tree, the thing works…

Equipment:
An Arduino-Compatible Mega 1280 Board: http://arduino.cc/en/Main/ArduinoBoardMega
    ATmega1280 Microcontroller
    Bootloader installed, ready to upload sketches from Arduino software
    Flash Memory 128 KB (32KB for standard uno)
    4 KB EEPROM

An Arduino Uno board would suffice for this project (binary sketch size: 22.9KB)
A W5100 Ethernet Shield V.6 Ethernet card