I pack light, and am on a quest to pack even lighter, but there are a few things that I bring "backups" of when I travel outside the US. So, if you were going on a week-long trip with no or limited access to shops, do you bring anything extra "just in case"?

Here's my list:
extra prescription medication
extra contact lenses
one normal lip balm and one w/ sunblock (or I would bring 2 regular ones...)
extra camera memory cards
hair ties -- I bring half a dozen and use them for random things as well as hair, but they break and I always have extras

For photography-heavy trips a backup DSLR
I always have a second camera battery but don't consider it backup since I use it.

I try hard not to be a "just in case" packer, but some things are so important and/or small that I don't stress it. What's your list?

I bring extra medication and batteries. I've never needed either but maybe some day.

Arguably the most important "back up" would be personal information including financial resources, i.e., all those NUMBERS with which we access our resources, when we're out of town, WAY out of town:

- drivers' license number and expiration
- passport number and related information
-credit card numbers including that rear code
-reservation locations, phone numbers and confirmation numbers

Of course, to the extent that we carry such, probably we should consider a simple CODE to minimize the risk from having such lost or stolen. As well, having these stored similarly on-line, accessible by an E-mail to ourselves, would be a further back-up.

Worst case scenario, you're victimized, and find yourself methaphorically or even worse, literally naked in Nairobi....what's your plan?

I would imagine that readers already have plans in place to deal with such, that they might share.

Yes to extra meds.
I have learned, from painful experience that my back will lock, when I least expect it, on a trip. I now take my just-in-case-back-kit. A heat wrap - back pain pills - mini TENS machine. I may not need them, which is fine BUT if I did, thank goodness I packed them, at least I can still move about and not cancel any plans during a trip.

Glasses, lip balm, back up camera, and camera batteries. I do stereo (3D) photography. I can't just pick up a stereo camera anywhere. I had one fail on me the first day of a trip once... heartbreaking!

I tend to go a LITTLE crazy when it comes to packing undies. If I'm going away for 4 days/3 nights, I'll end up bringing along at least 6 pairs of panties. It's silly, really, because I usually stay with family or friends (and thus have access to a washer/dryer) or can sink wash but they take up SO little space that it's worth it to me.

I tend to go overboard with OTC meds (Advil, Benadryl, Pepto, Lactaid) along with a few Lara bars. This is just in case I get stuck in an airport when concessions are closed, which has NEVER happened to me (*knock wood*). It has, however, come in handy when staying with friends and waking up in the middle of the night with a raging headache and not knowing where they keep their ibuprofen (if they have it at all).

By contrast, a man's underwear typically includes a pair of boxers or briefs, plus an undershirt, weight of the set around 10 ounces. For our pending overseas trip, my wife's underwear total will weigh just a bit more than one set for myself. To make CARRY-ON possible for trips of a week and longer, I have become a necessary convert to hotel sink-wash (using small packets of the Tide sinkwash discussed previously.)

I concur that carrying a basic set of OTC prn medications makes sense. These should include:
- ibuprofen, naproxen or acetaminophen
- acid blocker like ranitidine, omeprazole or such
- antihistamine
exclusive of any PRESCRIPTION items both regular and prn; controlled substances such as opioid pain medications and/or sleeping aids are a whole further topic...

i think this depends on a variety of factors including: personal or business travel, alone or with significant other, length of trip, and perhaps most importantly- location.
i don't find it neccessary to bring extra chapstick for a long weekend in las vegas. i may in fact bring it, not its neccessary.
on business trips solo, i don't bring copy of driver license. i call home to my wife if i needed that info. anything i use with batteries are aa or aaa eneloops.
i know some people who travel with their passport domestically. personally i don't agree with that.
i do think extra contact lenses and medicine makes the case for any travel scenario though.
and lastly, what kind of container(s) that those backup items are stored in, carried in.

Interesting. I had never even though of taking my passport or copies of my license when traveling domestically -- I think they're much safer at home. In general I don't worry about much at all when I'm traveling domestically (in terms of prep and what I take -- I'm always vigilant!)... even things like contacts, while I'll bring an extra pair, I don't stress it. If I needed to I could call my eye doc and get my Rx faxed somewhere near my travel destination, I'm sure. Same thing with Rx meds -- I take a little extra, but not a ton. Traveling out of the country where that stuff isn't accessible though turns be into a different travel person and I get quite concerned about making contingencies.

And I will also admit to taking 5-6 pairs of (women's) undies for any trip of more than 3 days... they are so small and light. Plus I often wear 2/day if I'm out walking/hiking during the day and then get to shower and change before dinner that night.

As per the initial poster, for traveling OUTSIDE OF THE US, I physically bring BACKUPS OF/JUST IN CASE:
1. 2-week disposable contact lenses (plus I keep a digital copy of my rx online via email; SO small and light it's ridiculous for me NOT to bring an extra pair or 2 or 3)
2. first aid kit (a pretty robust one, including a mini-pharmacy of numerous prescription meds and antibiotics that my doctor is fine giving to me; foreign medical systems are things I would really rather not experience unless it's an absolute life-or-death emergency)
3. camera (actually it's just my iPhone 5's camera, in addition to my separate point-and-shoot)
4. money (I always exchange dollars in the US for as much local currency as I would need to survive/eat/lodge for my first day abroad, in case my ATM and credit card somehow don't work locally when I arrive; that gives me a day to deal with that glitch and not be in dire straits)

That's it. Everything else can pretty easily be replaced somehow abroad, as long as I've got the funds to do so.

Being terminally myopic, never travel without a spare pair of eyeglasses. When I was thirteen, on a teen trans-USA bus tour, something dropped FROM the ceiling of the Henry Ford Museum in Dearborn, Michigan, and fractured one of my lenses. My parents had to get another pair made and air-mailed to our next stop. I NEVER TRAVEL WITHOUT A SPARE PAIR OF EYEGLASSES!

Oh, and to their credit, the Museum staff accepted my story, and reimbursed the cost. Funny what one remembers half a century later!

My extras list is pretty much the same as CoCo's. I tend to pack extra undies, although more so in the summer than winter. If you are hot and sweaty, sometimes switching to clean and dry ones can just make you feel better.
I also have a small kit that has extra OTC meds. Things like Benadryl, Lactaid pills, Alieve. Even when I travel domestically, this goes with me. You can usually find the basics anywhere, but I seem to only need them in the middle of the night! I'd rather just have everything with me. It is a small kit, the same size as my 3-1-1 bag actually and it stays ready to go for any trip.
I bring an extra set of contacts as well. I have found for domestic travel it isn't as necessary though. I buy my contacts through 1800-contacts and they've partnered with Walmart so if something happens, I can buy them there and they can easily access my prescription.
This site has actually taught me to cut way back on my "just in case" stuff. By actually writing out a packing list in advance, I've found I carry less and less stuff with me on every trip.
I think the only trip I over pack for now is car trips to our family farm. It is in the middle of nowhere and my dad lives down there with just the dog. The closest store is a nice drive, if it is even open. :)

Going to remote location as OP states, bring wheeled luggage, can't buy that replacement there.

I take a back-up pair of glasses, meds, xeroxed and laminated copy of my passport and driver's license, camera battery, and charger; depending upon the type of trip, I'll take a back-up camera.

In case I wake up naked in Nairobi, I scan my passport and driver's license and send it as a PDF file to my Google e-mail account.

If I will be going to a dodgey area, I alert the US embassy or consulate to my plans. If there is no US embassy, I've/We've had good luck with the Aussies; although, it does depend who is on staff and where you are.

- Backup copy of ID, credit cards and important contact info for replacing credit cards and IDs
- Backup copy of ticket and hotel reservations and important contact info.
- Extra meds, allergy meds, eyedrops and cold medicine enough to last a day until I get to somewhere where I can purchase what I need.

I always have a few alcohol wipes, band-aids, q-tips, a hair tie and 1/2-oz of Dr. Bronner's Liquid Soap in each travel bag ready to go. The Dr. Bronner's goes into my handbag to be used as handsoap. Alternately, I sometimes shave down leftovers-half-used bars of soap with a vegetable peeler and put the shavings into a Listerine breath strip container to be used as handsoap on the road. I like to be able to wash my hands whenever possible while on the road.

When traveling with a buddy, I always have an extra copy of their info and tickets as well.