I went to the WordPress extent page looking for a way to stop a category from showing in my feed as I don't want the single photo's I post to show up there.
The first plugin I found is awesome and does far more than I needed.
Advanced Category Excluder by DjZoNe is a simple little plug that lets you choose any of your categories to exclude from the archives page, home page, RSS posts, RSS comments or the search. This can be handy in so many ways and is worth checking out if you do need to block a cat from any of these points.