As Randy said, there are plenty of lists out there, but you need to build a bag to your specific needs. I used to rely on the trunk of my car for my "get home" supplies, but now I've got to carry everything in an EDC bag, so it needs to be lighter and more mobile. Your needs will vary.
The most important part of the bag is a PLAN. If something goes wrong, know what to do and how to go about doing it. Speaking from someone who was a block away from the blasts this morning, you don't want to be figuring things out when SHTF. You want to know what the Plan is and how to execute it. And then have a backup plan, if that doesn't work out. I think this is 100x more important than having stuff in a bag (especially in the city & suburbs, where resources can be plentiful).
That being said, this is my EDC/Get Home Bag:
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On my person I always carry my wallet, cell phone, folding knife, key chain with OC and my CCW.
I wear a practical pair of shoes to work (running shoes during the summer, boots during the winter) and keep my dress shoes at my office.
My bag is a Burton DJ Bag. I’ve gone through a lot of bags, and so far this one has been the best balance of utility and professionalism. Its heavy duty nylon construction is very durable, it has surprisingly good capacity, it can be worn as either a shoulder bag or backpack, and it’s very discrete.
In the bag I carry:
My lunch, generally leftovers from the night before (it amazes me how many people waste $10+ to buy their lunches out every afternoon).
About 1000-2000 calories of extra snacks (mix of Cliff bars, trail mix, gum, whey protein powder, vitamins, etc).
Britta water bottle with built-in filter. I know it’s not the best filter, but it’s practical for my purposes.
Change of clothes, seasonally appropriate (i.e. gym clothes). In the winter I’ll carry an extra base layer, hat, gloves & a few of those pocket hand warmers. In the summer, a bandana, ball cap and a small folded up rain coat.
Small toiletry kit with toothbrush & tooth paste, mouth wash, deodorant, baby wipes, etc and a camping towel. That towel is probably the second most used often item in the entire bag.
Emergency credit card (low limit), $200 cash (small bills), roll of quarters.
Emergency cell phone, cell phone charger with USB, car and wall plugs. It costs me $5/month to keep a spare flip phone activated on my plan, and it comes in handy quite often. I also carry an external battery which will charge my cell phone, GPS or other USB devices. This is the most used item in the bag.
Pocket tool (Leatherman), LED headlamp (much more useful than a flashlight), spare batteries.
Lightweight first aid kit (designed for backpacking) with a couple additions (Quik Clot, spare contacts, nail clippers, etc). Travel sized sun screen, bug spray, hand sanitizer.
Sunglasses, headphones, ear plugs, spare pair of eye glasses.
Spare magazine for my CCW.
Small notebook, pencil, pen, sharpie, length of duct tape wrapped around the Sharpie, compass, paracord, contractor trash bags and various small "survival" bits.
Waterproof map of the city, train schedules, location and phone numbers of hospitals, police & fire stations, rental car agencies, bicycle shops and bike rental stands, addresses and phone numbers of friends who live in the city and other key information. Basically anything I would normally rely on the internet, if cell phone service went down.
-Encrypted flash drive with scans of all my important documents - birth & marriage certificates, social security cards, medical records, financial records, insurance information, estate planning info, etc, etc. If I have to evacuate and can't get home, it contains everything I'd need to start over.
-Finally, I have a reflective vest with LED lights on it - you never know when you might be hiking home in the dark and need to stay visible.
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In general, try to visualize the situation, and walk yourself through everything you would do, and what you might need. If possible, give yourself a trial run - take a half a day off and hike home one Tuesday afternoon using nothing but your bag. This will help identify things you might need (like snacks and water) and things that are probably a waste of weight and space (bulky survival/camping gear).
Also be mindful that if you can't get home, or if your home is in an affected area, you may very well end up spending the night (or longer) in some sort of Red Cross or FEMA shelter. If you do, what would you want to have with you?