Unfortunately, there really isn't anything you can do about your oily scalp, as that is controlled by genetics.  You can however, try to find some solutions that will help you to better deal with it. 

Don't use shampoo for "oily" hair, as this can actually have the opposite effect and can be over-drying for the rest of your hair.  Experiment with different shampoos that don't contain harsh ingredients or anything that might aggravate your scalp and cause it to produce more oil to protect itself.  It's important to make sure you get your scalp very clean when you wash your hair (massaging your scalp gently will help to achieve this) but you also want to avoid over-brushing or any kind of over-stimulation of your scalp otherwise.  You might also try washing it less often... many times once your body gets used to this, it will begin to produce a bit less oil.  If the top of your hair gets oily and you don't want to wash the length, try dusting it with a bit of cornstarch at the roots and brushing it through with a boar bristle brush or tying the rest of your hair back and washing only the scalp.  I also suggest posting your question elsewhere on the boards if you haven't already, I'm sure others will have good suggestions as well.