DOWNLOAD & INFO PAGES
There are several sources for the ArduCopter project.
The first one is the official ArduCopter Wiki:
http://code.google.com/p/arducopter/wiki/ArduCopter_Quad
You'll find all basic info there.
Second one is Kinderkram's ArduPirates Build log:
http://www.rcgroups.com/forums/showthread.php?t=1286011
Meet an international community of copter enthusiasts there!
Download Page for the Arduino Software:
http://arduino.cc/en/Main/Software
For several OS like Windows, Linux...
Download of the Carancho Configurator 1.1
http://www.board-portal.de/ArduCopter/ArduCopterConfigurator_v1.1.zip
Download of the Configurator Update 1.22
http://www.board-portal.de/ArduCopter/Configurator-update-v1.22.zip