The Editorial Freelancers Association has a searchable database that's free for anyone to use. It allows you to use keywords, like "young adult" or "memoir," to find an editor that specializes in your type of writing. Many editors offer customized editing samples, and this is a great way to find out if you've got the right fit. Some writers like to use local people, so you can use a city as a keyword as well.
If you are an editor, or interested in becoming one, be sure to check out the North Dallas chapter of EFA.