A Removable Storage system provides two classes of media pools: system and application. System media pools include free media pools, unrecognized media pools, and import media pools. Removable Storage creates one free, one unrecognized, and one import media pool for each media type in your Removable Storage system.
For obvious reasons a camera is really nice to bring along. Big plus if it's a digital camera! Other items: a whistle, in case you get lost or need help ; waterproof matches ; some kind of lip balm/blistex ; sunglasses ; extra batteries for that flashlight! gaiters are great if you're hiking in shorts and it's a bushy or wet trail
I suggest reusing the plastic bottled water bottles, they're a good size and very lightweight when empty, and you can easily bring 3-4 for a longer hike. Water should be the heaviest thing in your pack and preferably easily accessible while you're walking.