I realize it is not Xbee, but you might look at these.
http://shop.ciseco.co.uk/rf-328-arduino-atmega-328-compatible-radio-transceiver-rfu-328/
Small board with radio module. Been playing with the larger version (UNO sized board) and they seem pretty good. I didn't find the chip arial very good, but with a wire whip the range seems good.