Sorry to revive an old thread. The AUX input on my 500C is next to the blue and me USB port by the front cup holders. Regularly use it to play my IPod although you can't use the in car controls to select music, this has to be done via the Ipod/phone etc.
EDIT: Added link to blue&me PDF
file:///C:/Documents%20and%20Settings/Admin/My%20Documents/Downloads/Quick%20User%20Guide%202.pdf