Hi. I would really like to have such a feature.
What I want to get is to have a lateral feed of my own news, that I do not want to go to main page where I would like to see only the main posts.
So I can post the "news" in a specific category (say, news...) and show in the lateral column in a RSS widget.
BTW, I could make this customising template but it does not worth to setup my own wordpress and get a host for just this feature... So it should be possible to uncheck one or more category marked post to go into main page.