I know the official wireless shield (xbee) is connected to the first port of ATmega328P (PD[0..1]). This is the same port where is connected the ATmega16 for USB connection.
Obiouvsly, if we want communicate to the xbee and send data to the pc at the same time we can't.
Not using that shield, with no other hardware, you can't.
Sparkfun sells a much better shield that allows you to switch which pins the XBee is connected to - 0 and 1 in one position, 2 and 3 in the other position.
You could use an FTDI cable to connect to two pins, like 2 and 3, and use SoftwareSerial to talk to the PC via those pins and the FTDI cable.
eg. 0-ohm resistors
They sell them by the spool at Radio Shack. They are called wires.