There is a reason that women (most, anyways) like having their ears nibbled, necks kissed etc....when women are aroused, most of the blood tends to concentrate in the upper chest/head area. For men, obviously, most of the blood heads down below, but for women it heads up above.
Consequently...nipples, ears, neck and what not are all very sensitive. I've had more than several girls tell me that kissing their necks or ears drives them CRAZY, and it's true. Definitely a good bit of stimulus to think about for next time.