I personally think that you may find it more convient to get a day pack for a number of reasons: More space and two shoulder straps. You may need to walk/evacuate longer distances, and having it over your shoulders on your back may be more confortable. Plus, it looks cooler. <img src="/images/graemlins/smile.gif" alt="" />

I purchased a North Face Neutron 32 backpack. It has 1 main compartment, with another exclusively for a 70oz Nalgene pouch. There is also an organization area for pens, pencils, keys, etc. Its gets full pretty fast. I have rain gear (jacket and pants, they both "store" into their own left pocket, pretty sweet), first aid kit, multitool, hat, water, snack, mini flashlight, glowstick, fox 40 whistle and lanyard, sunscreen, towel, water and spare set of glasses. On days I go to the gym, it gets real full with just my clothes. The sneakers are too big to fit in it, but in a pinch, I could attach them to the outside of the bag. Depending on where I'm going and what I'm doing, I can still add a hygeine bag (toothpaste, toothbrush, mouthwash, dental floss, razor, shaving cream, shampoo, comb, deodarant (currently a stick, need spray, doesn't hold up to the heat very well)), amateur radio HT, spare keys, and spare cell phone battery pack.

The only thing that I could really use, and probably could attach to the bottom of the bag, is a small tent, and perhaps a tiny pillow. With clothes and a towel, that may not be necessary.

It also features some "cinching" straps on the outside to bring everything closer to your back. Oh, it also has a place for a bicycle helmet too.

The North Face Neutron 32