To remedy the lack of sources (and hard numbers), I've started to write down here (for easier references) what is given for caloric values here: USDA Food Composition Databases.
Feel free to contribute. ALL CALORIC VALUES LISTED BELOW ARE IN KCALS FOR 100 GRAMS OF THE PRODUCT.
Pâté
Fish/meat in tin cans
(+) practically never spoils
(+) can be warmed on the fire very conveniently, no additional dishes needed Cooking/heating in cans is not recommended; they are not designed to be heated and tend to leach metals such as chromium and the plastic liners leach BPAs when heated. You can now get cans which have "natural" liners made from plant oils that are BPA free, which may be better, but the (scientific) jury is still out on this one.
(-) tin can difficult to dispose of - smells of fish, cuts skin very nasty, does not degrade if thrown away in nature (this can be remedied somewhat - tin cans can be transfered to sealed plastic bag using a vaccum machine and wouldn't spoil the product if done soon before leaving and under clean conditions) Also don't do this - you run the risk of severe food poisoning from a range of anaerobic bacteria (particularly Clostridium species) unless the food is kept below 4 C/39 F.
(-) quite heavy, considering the weight of the sauce and of the can
Caloric values: 198 for tuna in oil
Dried meat
(+) long-lasting - can last almost a month in the summer
(+) high calories to weight ratio
Caloric value: varies depending. For beef jerky, 288 kcal show up in a few different products.
Salami
(+) long lasting
(+) small quantities add taste to bland ingredients
(+) high calories to weight ratio
(+) can be used cold or cooked
(+) high quality artisan products are easily available in continental Europe
Caloric value: about 420 for artisan Italian Salami. Varies.
Dried bread
(+) high calories to weight ratio
(+) cheap
(+) good for your stomach (fibres)
DIY: Put oil and toss bread chunks for 15 min on 150 degrees centigrade in the oven.
Small packages of cheese, vacuum
(+) tasty
(+) healthy food
(-) not very long-lasting - at most a week in the sun
(-) Freezes in winter. Lasts longer but not as convenient.
Caloric value: about 400 for cheddar cheese. Varies.
Note: "Small" package means such that can be eaten up in one day. If the group eats together maybe even 1kg can be considered sufficiently small.
Chocolate
(+) high calories to weight ratio
(+) easy to eat on the go
(+) rapid energy - chocolate is both psychologically stimulating and quick to give off energy (however, it is not a substitute for solid food)
Dried fruits and nuts
(+) high calories to weight ratio
(+) healthy food - especially those, containing Mn (apricots)
(+) easy to eat on the go
(+) diverse - get as many different types of dried fruits and nuts as possible
Caloric value: Regular trail mix weights in at 462 kcal/100g.
Couscous
(+) high calories to weight ratio - it's much denser than most forms of pasta so takes up less space, and can be cooked using much less fuel
(+) easy to cook - Mixed with a packet of dried soup or even just chilli powder it's reasonably palatable, or you can chuck in anything else you can find (meat, veg, etc).
(+) Requires less water than many other cooked meals.
(-) needs to be cooked
Caloric value: 376 for regular, dry couscous.
Quinoa
(+) Excellent nutritional value and high in protein
(+) Easy to cook, goes with many types of food
(+) Lightweight
(+) Requires less water than many other cooked meals.
(-) Needs to be cooked
Tahini paste
(+) healthy food
(-) needs to be cooked - typically you'll want to eat it with something else, not on its own- and then you need bread, crackers, or something similar for it
Caloric value: 368
Military Rations
(+) long shelf life
(-) bulky
(-) More expensive than DIY
Survival Energy Bars
(+) compact
(-) not good day to day food - they turn to powder very easily
Marmalade, Jam
(+) tasty addition to the main food
(-) problems with storage - usually sold in massive glass jars, other than that this food has very high calorie to weight ratio
Potato paste
(+) high calories to weight ratio
(+) can be cooked or just dissolved in cold water
(-) not tasty unless mixed with something else and probably cooked
Potato Chips:
(+) high calories to weight ratio
(+) tasty: different flavours plus they use industrial taste enhancers to make the good more marketable
(-) low in vitamins and micro nutrients
(-) crumbles
Nido (dried whole milk)
(+) high calories to weight ratio
Cookies:
(+) high calories to weight ratio
(-) good desert, especially combined with nido or tea
Sunflower/Olive Oil
(+) can be eaten raw (with bread) or used for cooking virtually anything
Caloric value: 884
Lentils
(+) Do not spoil
(+) Good ratio of nutrition to weight - beside calories, they provide much protein and micronutrients
(+) Easily cooked, just like rice (unlike beans, don't need to be soaked)
(+) They pair well with the concentrated tastes of preserved food (e.g. salted meat) and with foraged stuff (thyme, sorrel, etc.). Less bland than typical carb food (rice, couscous) when eaten alone.
(-) need cooking (watch out for the type: some, usually orange/yellow ones, are quite fast, while others may need an hour)
(-) the tent will smell
Caloric value: 180
Whole wheat pasta
(+) Do not spoil
(+) Good caloric value for weight
(+) Easy to cook (preferably go for thinner & compact varieties, such as thin spaghetinni)
(-) Needs to be cooked. For winter camping, you can either make it a soup or else you have to waste the water.
Caloric value: 352
Instant mashed potatoes
(+) Do not spoil
(+) Pre-packaged
(+) No cooking needed, generally just add hot water, stir and let it sit for a minute.
(-) Generally not as calorically dense for the packing volume, e.g. compared to pasta.
Oatcakes
(+) long lasting
(+) high calories to weight ratio
(+) go well with cheese, spreads, salami etc
Caloric value: about 430.
Peanuts (or other nuts)
(+) long lasting
(+) Extremely calorically dense per weight and volume
(+) Easy to snack, easy to package
(+) No cooking needed
(+) Come in all varieties of unflavoured, salted, sweet, ...
Peanut Butter
(+) long lasting (not the 100% kind, though)
(+) highly caloric
(+) small volume
(+) comes in many package sizes, usually light but strong plastic jars with screw lid
(-) Usually requires something to spread it on
(-) Hardens in cold weather
Caloric value: 588
Honey
(+) does not spoil. (apparently literally never)
(+) small volume
(+) comes in many package sizes, including light but strong plastic jars with screw lid
(+) also serves as sweetener for tea/coffee
(-) Usually requires something to spread it on
Caloric value: 304
Boiled eggs
(-) spoil after 5 days or fewer
(-) not too caloric(estimates range from 75 to 135 kcal/100g)
(+) extremely healthy - ask any Sumo fighter
Some of those are not particularly unspoilable. I bring them, and even move spoilable food for the first couple of days for a hike. Eat fresh at the beginning, eat light at the end.
Regardless of what you bring, you should never keep them in original packaging. It is better to portion out everything while at home, rather than having to do it in the bush (easy to do when the sun shines, not as fun when it's raining cows). You also save the weight. The objective should be that every "package" is in its own ziploc bag or such. You just need to take it out & cook it or eat it.