user permissions in wordpress

Im curious as to how easily I can set user permissions in wordpress. I know I have author, editor, contributor, etc…but I was wondering if I can go deeper than that. For example, lets say I want someone to be an author, so they can write and publish posts to categories. But there are certian categories which I dont want someone to post to, for example, i’m using a magazine theme and I have “lead categories” and “feature categories” which I only want an admin to be able to post to and remove from. Is there any way I can only specify certian areas in which a user can post and only in certian categories in which they can post?

Thanks for your help!!!