Some things you probably already have that you just keep given Northern climates that most guys around here don't think about (NC). Kitty litter would be one of those. Other things I think IMHO every vehicle should have. A basic tool kit; jumper cables; some tire, transmission and radiator sealant;oil, water, and antifreeze; and possibly belts and hoses. Even if you don't know how to change the belts and hoses or preform any maintenance on the car, there is a chance someone may stop to help you that knows how to do the work but doesn't have the parts or tools. I wouldn't suggest going out and buying new belts and hoses just for this, next time you get them changed on a regular maintenance schedule (hopefully you're keeping up with this given how many miles you're driving) just ask the mechanic if you're getting the work done to save them for you and use the old ones. If you're in a pinch they will work. Staying with just my opinion the sealants are just a quick fix to get you some where to get a more permanent repair. The jumper cables can serve two purposes: if you need a jump and someone will assist or you happen along someone that needs a jump. The water can pull dual duty as well. Something to drink if you get stranded or coolant for the car. Keep in mind not to use straight water to fill a radiator, use a 50/50 mix of water and antifreeze. If you don't the water will freeze in the radiator somewhere around 15 degrees (it's lower than 32 because it's pressurized if I remember my schooling correctly).
A couple of "tricks of the trade" so to speak. I've been a mechanic for 10 years and an avid off-road, 4x4 guy, hot rod guy, since i was 14-15 years old. One quick fix for a coolant leak is black pepper. A pretty good dash of it in the radiator and refill of the coolant will get you by in a pinch. Power steering leaks can be fixed short term by adding a splash of brake fluid. Transmission leaks and sometimes it unable to shift (if it's full of transmission fluid, check that first) can also be fixed in the short term with a splash of brake fluid. Again this is SHORT TERM. After several days of running either of these systems with brake fluid in them the seals will burst. Literally, that's why this works is the brake fluid expands the seals so it makes the leaks stop or the transmission shift.
I'm sure there are TONS I'm missing more veteran guys will be able to say, or I'm sure you can look back through older post and see this question answered. Just thought I'd post this to help out. I'm new here as well and hope maybe the "tricks" can help you and others out.
Thanks -John