* The House-Elves: These servants work in Hogwarts and in the wizarding world in general. We see many house-elves, but none are particularly prominent in this book.
* Mrs. Figg: She is a squib (a non-magical person born to magical parents) who acts as a "neighbor" and watcher over Harry, but in reality is an Auror and a secret agent for the Order of the Phoenix.
* The Malfoy Family Servants: We see Dobby serving the Malfoy family, though he is more of a companion to Harry than a servant to them.
It's important to note that the concept of "servants" in the wizarding world is very different from the typical image of servants in the Muggle world. Many house-elves are treated poorly by their "masters," and the idea of being a servant is viewed as a negative thing.