The Official Arduino Wireless Proto Shield is the easiest way to add Xbee modules to yourArduino. This simple shield is designed to work with Digi Xbee Modules (or other modules with the same footprint) to give your projects wireless capabilities. The handy prototyping area lets you add circuits and sensors so you can relay data without wires or separate protoshields.
One great feature on this shield is the onboard serial select switch. It allows you to A) let the microcontroller communicate to the module, or B) let you configure the module with your computer through the USB port on the Arduino, eliminating the need for other adapters and cables. Very nice!