Are you looking for information to help you get the Xbee telemetry working, or are you looking for information on the MAVLink protocol subset that is sent over the Xbee (and any other telemetry link, including USB?)
Information on the former is at http://code.google.com/p/ardupilot-mega/wiki/Wireless or http://code.google.com/p/arducopter/wiki/AC2_telemetry (same basic info, one for planes, one for copters; I like to read both for the input and tips) with troubleshooting and reprogramming scattered around in the forums, and information on the telemetry protocol in Mavlink_Common.h, and http://www.qgroundcontrol.org/mavlink/start
There is more, but those are good starting points. Hope that helps!
I need to buy board for wifi module xbee pro for arupilot mega. I chose this .. i this compatibile with arduPilot Mega ?
sorry for my English..