I know a guy that does the whole raw thing and they use a dehydrator a lot. Mainly for treats etc. They are totally into balancing it out though and do a vege and pureed organ meat meal too. There are a few natural type diets that are commercially available that are dry.
Wysong (I think) has these freeze dried meat patties that my dogs just love. They are pricy and I haven't gotten them in a while.