Wordpress newbie private categories


although i’ve been developing for a while, i’ve just got into wordpress, and am playing round with themes after getting the recent sitepoint book.

One thing I would like to do is set up a private category, for example for customer testimonials.

I would like these not to be visible at all on my blog site, but would like to store them in wordpress and use simplepie to take recent posts from this category in a feed to my normal site

Whilst I can make individual posts private, it would be nice to make a whole category private, so that any posts within this category are automatically hidden from the blog.

Is there a plugin that anyone can recommend to do this ?