The xbox controller is already usb ready its realy easy to add a male usb Connector to the end of the cord. just find a usb cable from an old mouse, keyboard or something and some electrical tape, then cut the cordes and match up the colours, thats it.
Note: there will be an extra ‘Yello Wire’ on the xbox controller end, just cut it short as its not needed
Note2: the xbox controller also acts as a 2 port usb hub. with a little soldering inside the controller you can add two usb female ports for other usb devices. an internal USB storage mod would be cool