I see lots of answers about food and backpacks, but not much about developing your dogs' capabilities to contribute to your groups' survival.
I don't have much to brag about here. My current dog is the dumbest one I have ever had. Her trained skills are mostly in the area of not making extra work for me: rings a bell to go out, does her business in 1 spot only, stands on a towel until feet dry, and just now will also find and bring the wireless phone on request. And of course barks at approaching visitors unless she recognizes them.
She did surprise me on a road trip over Christmas by taking a written message in her mouth and delivering it to a specified person on another floor. The recipient was thrilled no end, but actually all my other dogs have done this, too, as well as carrying tools back and forth, etc.
So now we have: sentry, and messenger. And the sentry alerts I have used go beyond visitors, to include sounds I may not hear right away or from a distance, such as kitchen buzzers, telephone, garbage trucks, etc.
I suspect this dog is hard of hearing, and she is certainly hard of paying attention. We have done some basic SAR work on tracking, air scenting & finding human-associated objects, but I have trained a lot of dogs, and I don't think this one will ever focussed enough to be counted on.
She does love to play ball and retrieve objects from the water, and she is an exceptionally powerful swimmer. One idea I want to try out sometime is fishing with a gill net. I know it is possible to cast the net and draw it in single handed, but I when I think of a net suspended in the water from plastic float balls on the surface, I think it might be pretty easy to train a dog to help haul in the net by grasping the floats.
I will be interested in what roles others are using for their dogs.