Here's what I keep in the Tribute (keep in mind I'm the one who goes out and fixes the trucks when they break down, so I do carry a bit extra in the tools department and such.):
On the left side in the mesh pocket I have heavy duty shop towels, an umbrella, the covers for my fog lights, 55 gallon trash bags, bungee cords, and flares.
On the left side in-between the black box and side is a first aid kit, "grab and go kit", and two small come-alongs.
On the right side of the box is my bag of cleaning cloths and rags, but I can also use the bag in case I need to transport stuff or carry some supplies/tools. I also keep a spare change of clothes in there.
On the far right is a fire extinguisher and in the front is my ice scraper/brush.
Inside the black box is my tool box (the largest thing in there) on the left side is: jumper cables, a jumper box (basically a 12 volt battery I can jump a car off of if I can't get to the battery with the jumper cables), a crow bar, a fold up army style shovel, a small air compressor, tow straps, my trailer hitch, a hatchet, a blanket, and a Haynes guide to my truck. On the right side is cleaning supplies (quick detailer, trim shine, tire shine, glass cleaner, interior spray, no-fog spray) gunk/grease/bug remover, anti-freeze/coolant, washer fluid, and oil.
Close up of some of the above.
The "grab and go" bag. This has a Doug Ritter pocket survival pack (
http://www.equipped.org/psp/index.htm) that has been supplemented with added small gear, a candle, a flashlight, a folding knife, water purification tablets, toilet paper, a N95 dust mask, swim goggles (that are also prescription glasses), a magnesium/flint bar, a poncho, a 55 gallon garbage bag, two energy bars, and a space blanket.
The purpose of this bag is if I have to leave my truck behind if I'm out in the middle of the woods or something I'll take this with me. That way if I get lost or something I at least have some basic supplies to get me through a few days. Also, the dust mask and goggles are for when I'm going through old building we are looking to buy (part of my job) or if I'm ever in another 9/11 type situation, where everyone is getting choked by dust and debris.
This is what I keep in my center console. Thick gloves for when it's just plain cold, thin Kevlar (cut resistant) driving/police gloves for when it's cold and I still need dexterity, thin strong cord, a CB radio, a waterproof flare, a 12 volt to 110volt inverter, a packet of 10 one gallon bags (for car sickness or garbage), a gerber multi-tool, a Streamlight Scorpion flashlight, an extension cord (for when I plug in the block heater or the heater on one of the diesels, or if I just need an extension from the inverter).
This is the stuff up on my visor and in the sun glasses holder. A pad and pen (for phone numbers, notes, part numbers, ect), a Smith and Wesson rescue knife (seat belt cutter, screw driver, glass breaker), and a Benchmade rescue hook (seatbelt cutter, bottle opener, regulator wrench, single "brass knuckle" when used with sheath)
Not shown: The two D cell LED maglight in the door pocket (good for beating someone with), the bottles water and food behind the seats, and the tire pressure gauge in the pen holder.
As to the tool box and first aid kit, I'm not going to list everything in there since it's a lot of stuff. But lets just say they are both are well stocked with good supplies.
Now I carry a lot of stuff because I often go to help others and I like being redundant. For example, I have three flashlights plus the one I carry on me every day. I'm not saying you need three. However, I am saying it's a bad idea not to have at least one. Even if you are too lazy to put together a kit Walmart sells these "Justin Case" pre-assembled kits that have a lot of stuff. While most of it is low quality it's better than nothing.
My recommendation is go get a small back pack and put some supplies and tools in there. It takes up very little room and can have just about everything the average person will ever need. Also, make sure to check batteries in flashlights, phones, radios, ect as they will go bad even just sitting. Usually I go through everything once a year and check it all over.