Just chiming in to say we would also very much like to add a link to Categories from the top-level of the side bar. Our users are not finding it in the Special pages.
Michelle
Please help me I have spent two days trying to figure out how to edit the sidebar to remove some links change the text and add a new catagorie link to it. I dislike the Random page, my watchlist, and other items, but the preferences and documentaition has nothing on it.