I've known a lot of witches who throw around that term, and their "familiars," are still but common animals--just as shitty as their owners. So I'm going to shy away from the term here. But it is totally possible to do some interesting "spells" on things--people, animals, plants, inanimate objects. In my experience, it isn't terribly difficult to do basic things like minor healing, causing unnatural longevity, and granting extraordinary strength and agility. I'm sure that a more adept practitioner could do more impressive things like transmigrations, shared perception, and the sort. Check out the meditation and witchcraft sections on JoS.
