Types of Long Shelf Life Foods

Packaging
#10 Cans	These cans are slightly smaller than 1 gallon paint cans (3.8 liter). When properly prepared (mostly by a combination of removing excess air, inserting nitrogen, and/or putting in air absorbers, and sealing them properly), the food can in some cases last 35 or more years.
MREs	MREs (Meals Ready to Eat) are not freeze-dried or dehydrated, so do not even require water to be added, so they take up the most space. They typically last 5-10 years or longer, if stored properly. The main disadvantage is the extra space they take up.
Pails	These are usually a 6 gallon size (23 liters). They hold a lot more than the #10 cans, and are cheaper. However, air can easily get into the pails. Therefore, only certain foods (such as grains) are suitable for pails.
Pouches	You will most likely want to avoid pouches, as they have a shelf life of about 7 years, rather than the 25+ years that the #10 cans are able to provide.
Retail Packaging	This is the type of packaging that you see at stores, that your food normally comes in. In most cases, you would only want to buy food in retail packaging if you plan on rotating your food (so you use food before it expires, and replace it with new food).

Brands
Mountain House	The most well known brand is Mountain House. Mountain House foods have been available for over 35 years. Their prices are a bit higher, but all their #10 cans have a proven 25+ year shelf life, they do not require cooking (heating is recommended, but not necessary), and they have a wide variety of entrees unavailable elsewhere. One big plus with Mountain House is that they sell a lot to backpackers, who eat the food (so it must taste decent!).
Provident Pantry	The Provident Pantry line appears to be a private label, possibly made by Thrive, for Emergency Essentials. They claim a full 25 year shelf life for their foods, and their foods are priced well.
Provident Provisions	The Provident Pantry line appears to be a private label, made by Thrive, primarily for Emergency Preparedness Center. They do not provide servings per container or calorie counts, making comparision shopping very difficult. However, since they appear to be the same as the Thrive brand offerings, it may be safe to assume that the servings per can and nutrition information are the same.
Saratoga Farms	Saratoga Farms appears to be a private label, made for and sold by The Ready Store. The retail prices tend to be somewhat high, but there are often sales and/or discounts.
Thrive	Thrive is a brand sold by Shelf Reliance (and appears to also be the manufacturer of the Provident Provisions and possibly Provident Pantry lines). Many are inexpensive. However, the shelf life of the Thrive products vary quite a bit (some as little as 3 years), and many require cooking or other preparations.
Yoders	I do not include this brand in the lists here, since I cannot find any nutrition information for their products. They are made by the Amish, and have raw meat sealed in the #10 cans, at which point they are cooked. Presumably, since they are cooked after sealing, any living organisms would not survive. If you are considering their products, you may want to first read reviews online first.