I've made a few including the tomato skin powder Plot1 mentions. You can put almost any dried herb, fruit or veg in the multi-processor to make a new ingredient.
They can go in bread, hm pasta, white sauce bases and all sorts of other stuff. They pack a punch, so be sparing, especially with herb ones.
I've made mushroom powder whenever I've seen punnets of mushrooms reduced and was given some made from giant puffball. Both are excellent.
If you want pasta flavourings, you can dry stuff like spinach just by putting raw leaves in the dehydrator and drying like you would herbs. Adding powder to a pasta dough is much easier than trying to get wet ingredients in