I carry whatever messenger bag I think is cutest on any given day. Lately I've been carrying one with Pucca and Garu on it.
It always contains: A small makeup bag (eyeliner, quad shadow compact, lipgloss, concealer, mascara, tweezers, comb, ponytail holders), My DSi, a book (this week it is Flowers for Algernon), ipod, earbuds, small notepad, pen, my keys, a transit map, my wallet, advil sinus, cigarettes and lighter. I travel fairly lightly.