Bungee cords. The three black ones go around the pack, the net goes around again for extra security, the red ones go on the atlas bag and the plaid one goes on whatever. It's been with me on both my big cross country trips so it kind of just has to go. Call it superstition...
This bag and the one below go in the exterior pocket for quick access if I need them on the road.
In this one: kleenex, Goody's powder and Excedrin
And this one: sunscreen, chap stick, hand sanitizer and bug spray.
A few emergency items: Hot Hands (thanks Joshua), a space blanket, duct tape, paracord, matches and striker and a glow stick (in case a rave breaks out). These are in the larger outer pocket.
The other thing I carry is food, usually a couple cans and dry items. Soups, Beef Stew, Chili and similar canned goods are all good because they are easy to cook and usually available at a convenience store. Beanie Weenies are a staple since they are pretty decent cold if I don't feel like getting out the stove, waiting on the fire, or just want food immediately. Jerky and trail mix also do good. I also keep an aluminum water bottle in one of the side mesh pockets of my pack.