I dislike the traditonal directory because they seem to be little more then search engine spider food. When the web was a lot smaller traditional directories had their place, because search engines like google where not around. If you want to get user participation, I think you are better off to create facebook groups or blogs which cover your niche target. With a facebook groups or a blog you will get users which have similar interests as yours. Indirectly a blog is a type of directory since you have a blog roll and you often will be making posts which refer to other sites or blogs which are related to you. Possibly a blog linked to quality sites with good descriptions might be a better way to go. Anyway just my thoughts.