I never pack until the night before, because I'm still doing laundry! It always seems like we need to take stuff we use regularly, so I do a couple of loads the night before and check off my list as I go. I can then easily add the last few things in the morning.
Even though I don't start packing, I DO start tracking down all those little things I know I"m going to need, and put them in an easy to find place. So we leave next Saturday, and I've starting finding our lanyards and pins, autograph books, stockings I need for my Halloween costume, etc.