If I'm running from PDFs (which is often, these days - saves a lot of wear and tear on physical books), I bookmark up the PDF with Good Reader so I can jump around to the most relevant stuff of the current chapter quickly and easily.
I bring a small whiteboard for initiative tracking
A compartmentalized box of some sort for my pawns/tokens/paper minis
A Word document printout of all of the encounters - enables me to write on them as needed and track hit points and other forms of damage/conditions - plus generating it in the first place makes sure I've reviewed all of the encounter creatures/traps/stats