It's currently not possible to link to a category without making that page a member of it (See http://test.wikipedia.org/wiki/Category_issues#How_to_link_to_category_witho...).
This is a bit of a problem of course, Brion proposes a separate link table for category-member links as a solution. This would also allow to add a field that records the date when a page was added to the category which would be very useful for sorting category overview pages by date.
This would be hard to change later, so i'd like to start some discussion on this now before the category feature goes live.
Gabriel Wicke