Sticking a discussion to the top of a category
I'd like to be able to stick a discussion, or announcement, to the top of the list of discussions in it's category. A sticky or pinned post, other forum software might call it. I believe my google-fu has deserted me today, as I can't see anyone describing a method - unless it's just not possible? I can't see a plugin to do it, either. It's the last thing on my list to get a forum ready!
All help, advice etc gratefully received.