WordPress has a nice feature that allows you to password protect certain posts so that only those you share the password with can read it. This plugin improves upon that idea by hiding the post unless the person entering your blog has been assigned a particular level.
With the ViewLevel plugin, you can make certain posts visible only to registered users – or only registered users with at least a specified minimum user level. You could, for example, set a very private post to be visible only to those with user level 8 or above; a not-so-private post could be visible to those users level 3 and above, and a public post could still be visible to everybody. Users who aren’t allowed to see a post simply don’t see it – they don’t know what they’re missing!