Chilled! If you need to chill it quickly, stick it in an ice bucket or the sink. Fill with ice and cold water and twist the bottle back and forth in the ice bath. This is probably something everyone knows about, but for some reason it didn't occur to me until recently that adding water to the ice would speed cooling)
Unless you are my MIL and like the "bite" serve it chilled. It shouldn't be too cold though. Chardonnay should be just below cellar temperature...which I think is 65 degrees. If you have it in the refrigerator for an hour or the freezer for a half hour, it will probably be the right temperature.