(1) Handheld GPS with preprogrammed addresses for various WWDC events. Yes, I have a GPS built into my iPhone. Garmin hand-held GPS is better.
(2) Laptop, natch.
(3) External USB hard disk, for copying stuff around.
(4) iPhone, headset, chargers for both.
(5) Kindle, for reading on the plane.
(6) Business cards.