CAR KITS

BeReadyUtah.gov suggests the following items for car kits:
Driver's License
Auto Registration
Proof of Insurance
Gasoline Credit Cards
Traveler's Checks
Auto Club Service Card
2 Flashlights & Extra Batteries
Flares and Hazard Reflectors
First Aid Kit with Manual
Extra Car Keys
Litter Bag
Sunglasses or Umbrella
Cell Phone w/ adapter or phone card
Portable Radio & Extra Batteries
Fire Extenguisher (5 lb. A-B-C Type)
Extra Fuses
Jumper Cables
Jack, Lug Wrench, Tire Gauge
Basic Tool Kit and an Ice Scraper
Small Folding Shovel
Sand for Traction (Winter Season)
Duct Tape & Electrical Tape
Gloves, Rags, Paper Towels
Waterproof Matches
Contact Phone Numbers
Detailed Maps
Whistle & Small Mirrow
Pen, Pencil, Paper
Cash (Small Bills & Coins)
Drinking Water
Non-perishable Energy Foods
Can Opener
Medications
Toiletries
Blankets (Myler) or Sleeping Bag
Pack Personal Needs

Another car kit list that I have suggests the following items:
Warm clothing--hats, mittens, coats, warm pants, walking shoes and rain coat
flashlight - radio (hand crank)
4 ply plastic, (large piece)
portable water purifier
First aid supplies

A few other ideas are:
Portable Jump Starter & Air Compressor
2 Flashlights - 1 small and 1 large (The large flashlight is adjustable and can be set down. It is perfect for making repairs or changing a tire in the dark)
Whistles, Ponchos & emergency blankets (I have 1 for every seat in my car)
Compass
Roll of toilet paper
Medications - (I try to include the following medications in my first aid kit: pain/fever reducers, allergy meds, antihistimine cream, sting relief, extra prescriptions. I also include extra band-aids.)
Garbage bags and ziploc bags (multiple sizes)
Wool blankets
Extra Clothes
Hand Sanitizer &/or Wipes

Consumerreports.org also has a list of recommended items.