TIGI Bed Head Rockaholic is the ultimate dry shampoo. It comes in an aerosol can and sprays like a hairspray, but it helps you go longer without washing your hair, and fights greasy/oily bangs.
At the sight of grease, spray it directly on your roots and grease-B-gone! Rockaholic also lifts your roots higher to get more volume, and creates hold for those of you who like to tease your hair!
You can pick up a can of these for about $12.95 at most salons and beauty supply stores.