Some of my finds so far:
Nido powdered whole milk. Made by Nestle. Walmart and many other stores carries this in the Latino food section. This has excellent taste and works great in all kinds of mixes and as an emergency substitute for milk in cereal etc.
Nestle Media Crema. Again in the Latino food sections. This is small can of shelf stable cream. Use it in soups & sauces etc, and you can even mix it with a one or two teaspoons of white vinegar for a sour cream substitute.
http://www.minimus.biz/ Has individual packets of condiments etc. Salad dressings, lemon Juice, oriental sauces, barbecue sauce, half & half, mayos, mustards etc
Bear Creek brand dried soups are excellent, and carried in many grocery stores.
Gossner's Dairy (Utah/Idaho) has shelf stable milks... regular and flavored in both small and qt packs. They also have shelf stable cream in 8 oz boxes. I don't know if they sell online. This may only be available locally.
Hoosier Hill Farm (via Amazon) has many powdered products in 1lb amounts. I have tried their sour cream pwd and their blue cheese pwd. I have only cooked with them so far and they did very well. I haven't tried them as a dip or sauce but should work okay. The sour cream is not as tart as I expected. The blue cheese has good flavor and is quite strong so a little goes a long way.