RaspberryPI with Xbee ?

Hi, what are the easiest options to connect RaspberryPI with Xbee ?

I would have to say the best way is to use an XBee Shield from either Adafruit or SparkFun. Then connect the XBee to the Shield, then the shield to the Pi.

Thank you very much

Can i just use USB to connect it? Did i need some library?