This is my bag that I keep in my vehicle so I have it with me whenever I go away from the house. I use this bag in addition to my EDC items that I carry in my pockets.

Things I never leave home without .. small 7 LED flash light, pocket multitool, cellphone, razor knife

I take this bag with me whenever I go anywhere "off the beaten trail", like taking the kids for a hike or scouting a new area to hunt. I even take it with me when we just go for a bike ride through the park.
Thankfully I have never had to use any of these items in an emergency scenario (and I hope I never have to) but it brings great peace of mind to know that I have them with me if I need them.

Like mom liked to say every time I balked at having to take a sweater or jacket with me on a nice fall day .. "it is better to have it and not need it than to need it and not have it"

Step 1: Bag Overview

When I started out I knew I wanted a bag that either came with or had space for water bottle(s). With a little patience and a little luck I picked up the main bag for a few bucks on eBay. attached to one of the zipper pulls on the main pocket is a clip on flashing LED. I bought it to use when i walked my dog at night but he hates it so I found a new use for it. It makes a great high visibility signal at night to mark your location. (but it is a pain in the but to try to get a picture of .. it took me 7 tries to get one when the light was flashing)

The side pockets are small camera bags that I picked up at the dollar store. Right now the two that I have fit my needs but if I need additional space down the road I can always go buy a few more and slide them onto the main belt.

You will notice that I keep alot of things stored in ziploc bags inside my pack. There are 2 reasons for this. 1) it helps to keep thing organized and uncluttered 2) it gives me lots of extra containers to use for collecting things like forage foods or additional water should the need arise

I sort my supplies into 4 main categories

Shelter / fire
First aid
Food
Multifunction

Shelter / Fire
Compass
Emergency Blanket
Fire Starters
Flashlight
Lighter
Wire Saw
Whistles

First Aid
Assorted Band-aids
Crazy Glue
Gauze
Latex Gloves
Medical Tape
Neosporin
Tweezers
Alcohol Wipes

Food
Bullion Cubes
Drink Mix
Fishing Tackle
Salt and Pepper
Sugar
Tea Bags
Water Bottles

Multifunction
aluminum Foil - cooking pan (wrap foil over a forked stick to make a frying pan), fishing lure (wrap a small bit of frayed foil around the top of a fishing hook), trail marker (cut or rip into strips and hang at eye level. waterproof, easily shaped, reflective for highly visibility, use a sharpie to note direction of travel date and time), funnel

Bandana - Hat, Headband, Dust Mask (or as i like to call it "playing cowboy train robber"), Wet and wear for Hot Weather, Pot Holder, Collecting Wild Edibles, Sling (first-aid, weapon .. pick your favorite definition), Cordage (strips or as is), Washcloth/Towel, Dish Rag, Napkin, Pre-Filter for water (like Coffee Filters), Clean Glasses and other lens, Bind a stone and toss a line over a limb, Tourniquet

Black Trash Bags - container for gathering water or edibles, tube tent (open the bottoms and combine 2 bags with some duct tape), poncho, waterproof sleeping mat

Chapstick - preventing painful chapped lips, combine with tinder(Q-tip, non synthetic cordage, small bits of fabric) to make a longer burning fire starter

Duct Tape - I think we all can come up with 101 uses for this wonderful material.

If you have never heard of duct tape allow me to read to you from the holy scriptures "Yea, though I walk through the valley of wibbly-wobbly things, I will fear no shimmies: For thou art with me; Thy glue and thy fabric backing, they comfort me. Thou securest all things that shouldn't be moving." *passes around the collection plate*

Hand Sanitizer - banishing nasty hand germs back to the third plane of hell, fire starter (see chapstick for ideas)

Mirror - daytime signaling, seeing things you can't normally see .. like your face (handy if you accidentally walk into a tree branch with your head and get cut.. not that that has ever happened to me *innocent face*)

Multi-tool - depending on the tools included in your multi-tool will determine what it can be used for. The one I have in my pack has pliers, 2 sharpened knife blades, bottle opener, 2 flat head screw drivers, Phillips head screw driver, fish scaler/hook extractor)

Nail Clippers - trimming hang nails or cleaning up broken fingernails so they stop snagging on everything (if you have ever experienced this .. you know what i mean), clipping fishing line

Q-tips - cleaning boo-boos, fire starter

Razor Blades - i know this is a stretch .. but bear with me on this one .. cutting things .. I know,I know .. it's sounds crazy, but it is true. cut cord to make a shelter, cut up bait for fishing/trapping, cut up food (either what you forage or if you are successful fishing/trapping), go all Aron Ralston and lop off an extremity pinned under a boulder.

Towel - see step 3 "side pocket 2" for complete description

Twine - constructing a temporary shelter (tube tent, lean-to), Trap making, fire starting, fishing(extending your existing fishing line or improvising if you don't have any)

Zip Ties - shelter building, securing items to your pack, temporary handcuffs .. oh wait .. that's a different instructable

Step 2: Side Pocket 1

In the front pocket I keep a small steel mirror in a protective plastic sleeve attached to the bag by a small metal bead chain

Inside are assorted things to make water taste better

packet of powdered drink mix

Since any water that I don't bring with me is going to need to be boiled in order to make sure it is safe to drink .. might as well make use of the hot water i have.
several flavors of tea kept dry in a ziploc sandwich bag
a package of bullion cubes (aka instant soup)

Step 3: Side Pocket 2

I must defer to the great and powerful Douglas Adams for the perfect description here ..

A towel, it says, is about the most massively useful thing an interstellar hitchhiker can have. Partly it has great practical value. You can wrap it around you for warmth as you bound across the cold moons of Jaglan Beta; you can lie on it on the brilliant marble-sanded beaches of Santraginus V, inhaling the heady sea vapours; you can sleep under it beneath the stars which shine so redly on the desert world of Kakrafoon; use it to sail a miniraft down the slow heavy River Moth; wet it for use in hand-to-hand-combat; wrap it round your head to ward off noxious fumes or avoid the gaze of the Ravenous Bugblatter Beast of Traal (such a mind-bogglingly stupid animal, it assumes that if you can't see it, it can't see you); you can wave your towel in emergencies as a distress signal, and of course dry yourself off with it if it still seems to be clean enough.

More importantly, a towel has immense psychological value. For some reason, if a strag (strag: non-hitch hiker) discovers that a hitchhiker has his towel with him, he will automatically assume that he is also in possession of a toothbrush, face flannel, soap, tin of biscuits, flask, compass, map, ball of string, gnat spray, wet weather gear, space suit etc., etc. Furthermore, the strag will then happily lend the hitch hiker any of these or a dozen other items that the hitch hiker might accidentally have "lost." What the strag will think is that any man who can hitch the length and breadth of the galaxy, rough it, slum it, struggle against terrible odds, win through, and still knows where his towel is, is clearly a man to be reckoned with.

also in this pack is the towel's little brother .. the bandana

Step 4: Water Bottles

The bag holds 2 water bottles. each metal water bottle holds 3.5 cups or 28 oz. To me, fresh water tastes best so I change the water and wash the bottle out if I haven't used it in 2 weeks.

The nice thing about using metal water bottles instead of nalgene is that these can be used to boil water.

Clipped in with the water bottle on one side is a full sized sharpie marker. If you get lost staying put is the best option, but if you have to move Sharpies are great for writing on all kinds of surfaces if you need to leave notes (like what direction you intend to head and a time and date to make it easy on those trying to rescue your butt)

In with the other bottle is a lifegear glow stick. We originally bought these for the kids for when we go camping since they were a combination of flashlight, glowstick, and whistle all in one. It kept the kids from snatching up the good flashlight and then forgetting where they put them. In addition they come in lots of colors so we can color code the kids and tell which one is where even when it gets dark. The whistle is there if they get hurt or lost.
according to the product labeling you can get 12 hours of continuous flashlight use, or 200 hours of emergency flasher. The ones we have in our camping gear have made it through 3 long weekend camping trips and are showing no signs of slowing up. I bring replacement batteries(ag13/lr44) with me just in case but so far they have not needed it.

Step 5: Front Pocket

Front Pocket contents
Multi tool - tools vary depending on manufacturer
Magnesium Fire starter - scrape off some shavings, apply sparks, watch the world burn
fire starter with striker - pretty spark shower to get your fire going
vaseline infused cotton - heat vaseline in a double boiler until it liquifies. Sop it up with a cottonball and squeeze out the excess. Once it cools stuff the cottonball into a drinking straw and crimp the ends shut with a hot pair of pliers. To use take a small bit out of the straw and fluff it out. Add sparks.
chapstick - cherry flavored :)
matches in a waterproof case - wooden matches in a watertight container. Striker from a book of matches tucked into the lid.

Clipped onto the front of the bag
Compass - GPS is fantastic, but if you can't get a signal or your battery runs out, it is great to know an alternate way to navigate.
Mini sharpie
small LED flashlight - the only thing i don't like about this is you have to hold the button to keep the light on. But I generally have more than one flashlight at all times so it is a moot point.
stainless steel keychain lighter - it is like a zippo and medicine pill keychain spent a drunken night together and this is the result of their unholy union

Step 6: Main Pocket

Main Pocket Contents
Hand sanitizer
3 heavy duty black trash bags
Emergency blanket
3 sheets of heavy duty aluminum foil
wire saw
2 fire starter sticks - sawdust and wax compressed together. great for getting damp tinder started.
50 feet of duct tape - i used a bamboo skewer as a core to wind the duct tape on
Dental floss - nice strong cordage with lots of different uses.
Zip ties
100 feet of 150lb test nylon string
Replacement utility razor blades for my EDC knife
Condiment pack - just because you are in a rough spot doesn't mean you have to be a savage - salt, pepper, sugar, stevia, and mustard packets
First Aid Kit - see next step for details
Fishing Kit - Split shot weights, 50ft 10lb test, 50ft 14lb test, 2 bobbers, 2 artificial worms(1 is used to store the hooks to avoid accidentally getting stuck by one), 4 hooks and leaders

**update 11/30/2012**
I added a spool of wire to the main pocket - pictures and details will be added ASAP

Step 7: First Aid Kit

First Aid Kit
Container for wound care
Small container with 6 pairs of latex gloves
Q-tips in a ziploc bag
sanitizing hand wipes
3 inch wide gauze roll
1 inch wide gauze roll
Basic box cutter that uses single edged razor blades and replacement blades
Crazy glue
tweezers
Assorted sized band-aids

Wound Care Container
Alcohol wipes
medical tape
sterile surgical blade
iodine wipe
povidone-iodine wipes / gel
bacitracin
neosporin

Assorted band-aids
large and medium sized band-aids
butterfly band-aids
button band-aids
essentials of first aid pamphlet
nu-gauze pad
really big band-aid

Step 8: Things I Need to Add

Small sewing kit - for fixing popped buttons or tears ( no one wants to be rescued with their heiney hanging out because their pants were torn or falling down), in worst case scenario .. for suturing (good luck with that one rambo)
image courtesy of http://www.rhl.org/Content/SiteB/SWNGKITLG.jpg

Wire - for making small animal snare(if you know how to), a stronger binding if you think the twine wont hold
image courtesy of http://www.rktraplineproducts.com/16gtw.jpg

Suspenders - my bag does not weigh much, but suspenders will help to redistribute weight to make the bag more comfortable for extended trips. Also, it will give me additional places to attach things should the need arise.
image courtesy of http://jayleigh.files.wordpress.com/2008/07/mork.jpg

*update 08NOV2012*

Keychain CPR Shield - Vertical0001 made a great observation of something that I overlooked. A CRP shield in case I have to give CPR to someone I don't know .. or worse if someone needs to give me CPR. In this age of communicable diseases there is no reason to take unneccessary chances. image courtesy of http://www.funcpr.com/productspage2.htm