Keep gas tank full (refill at 1/2 tank)
1 gallon water
High energy protein bars
Keep the food out of direct sunlight, so it lasts longer.
First aid kit
Fire extinguisher - CO2
Metalic blankets
Flashlight/siren/radio combination
Sun logo emergency kit, in the SunWear catalogue
Swiss-army knife, or better yet a good folding blade knife with a 3-4" blade
A big knife
Maps of the area
Couple of MRE's (MEALS, ready to eat)
Small backpack to carry it all in
4-5 D-cell Maglite with krypton bulb or 2 AA cells mini-maglite- Extra bulbs
Road flares
Sealable plastic bags
Critical medication
Tissues
Pre-moistened towelettes
Tools - screwdriver, pliers, wire, knife
Spare Clothing
Poncho
Warm, all weather jacket (A mil-surplus field jacket is great because it's windproof, has 4 big pockets, a built-in hood, removable insulating liner)
Long sleeve wool sweater
Warm pants
Warm shoes
Rugged gloves (cheap mil-surplus leather gloves and removeable wool liners are great. For upscale folks, a set of deerskin black leather gloves with wool liners from Eddie Bauers.)
The nice thing about military clothes and stuff is
a) it's rugged and b) it often is inter-designed to work with other components (Ex: the M-65 field jacket has fold out wrist liners to be cinched down by the military gloves). Knit wool cap
Money (small bills/change)
Toilet paper
Tissues
Tampons or pads (useful for first aid, also)
A few large black plastic bags (environmentally incorrect, but very useful)
Vitamins (at least C since fresh food may be scarce for a while)
Spare glasses (if you wear them)
Gas siphon - or short rubber hose
Tow chains, tire chains (4)
Tent
Shovel
Chemical lights (Cyalume)
Walkman/batteries