Great suggestions! My DH makes fun of me, when we go on a day trip at some of the things I insist on taking.

I used to store extra big packs of TP in the trunk of my car when I lived in an apartment I figured if something happened and got stuck on a highway I'd make a lot of money selling some of it haha

Most of that makes a good start. Not sure about the rationale of some of it though but you pick and choose what's appropriate for your needs and area. Couple other thoughts, some of which were on the other thread:

A seatbelt cutter. Some now will attach right onto the seatbelt so if the seatbelt jams you can cut and exit quickly.
Medications, extra eyeglasses, and other special needs
A charger for that cell phone
I always keep some money but use change. Keep $10-$15 or so in quarters for parking and other incidental needs.
Some basic hand tools & a set of folding wheel chocks are nice
Tow strap/rope/chain, shovel & a come-along are good ideas too
And in the northland you don't want white rags for a signal - you want red, lime green, fluorescent orange or something that can be SEEN in the snow! I don't want to surrender, I want to be FOUND!
Current proof of insurance
A disposeable camera is a good idea but a digital camera with batteries is a far better idea. They're not as susceptible to the temperature extremes as are film cameras. If you're in a southern climate and leave a film camera in an enclosed vehicle it's ruined in a short time. In freezing weather the film emulsion can crack and spiderweb as you advance the film unless you warm it up adequately so the film is soft.
I carry a tarp. Multi use. For when you have to crawl underneath the vehicle, cover something or whatever. Takes next to no space. I guess you could use it for privacy, but if you're in trouble around people, isn't that a good thing? And if you're stuck in the middle of nowhere I think there's enough privacy isn't there?
Pen, paper & Purell
Sunglasses, spotlight and digital recorder
Aspirin, IB, etc
12v air compressor, extra oil, antifreeze and washer fluid
Tire pressure gauge, Ice scraper & snowbrush Sometimes some softener salt and the spray deicer is great
Battery charger and extension cords are occasionally priceless
If you have a pet, and are going far, keep copies of immunization records in case of a bite or if the animal gets sick
Item #c could be very bad advice. Be sure to check with the law enforcemnt agencies in your area before you do this. Around here if you call the station phone number requiring a reasponse, you will have to hang up and call 911 to get it handled through dispatch. THE CLERK ANSWERING THE NON EMERGENCY NUMBER CANNOT DISPATCH. If it's an emergency, it could make a big difference. So I'd be careful before advising this. If you just need to know what hours they're collecting for something, that's a different story, but I don't know of many people who would worry about that when they're broken down!

I use my cell phone as my address book, but as said I still print out one and keep in there. I have people's numbers I can call and even have some mechanics numbers. With a cell phone, ASSUMING YOU HAVE COVERAGE, you can call someone and get a number. A friend broke down about 100 miles from home about 2 weeks ago. The timing belt broke in his car. He called a number of people before he finally got his daughter who looked up numbers for a tow truck. Why he didn't call 911, I have no idea, but that's the way he is! LOL

One other number that I never see mentioned that is an excellent resource is a good library's reference desk. They will look up phone numbers for you, resources for you, and can provide a wealth of other information. This is one you shouldn't overlook.

I just thought of another hint I read. carry an old umbrella and an old non-see thru shower curtain. Then if you have to "take a trip to the woods" and are very shy you can hang the umbrella from a brnch and the spokes should fit in the shower curtin holes making a kind of privite potty for you.