WordPress notifies the admin of a blog when a comment requires moderation. This is done regardless of the author of the post who does not get a notification at all (of moderated comments). I wrote a very simple plugin for WordPress that notifies the author of the post as well as the admin of the blog when a comment requires moderation.
The plugin also assumes that you have moderation notify turned on in options. If the admin is the author of the post, he/she receives only one email.
Installation is as simple as download, unzip, copy to wp-content/plugins and activate. This plugin is running on this blog and has been tested on all 2.x versions of WordPress. Please submit bugs and suggestions.
Update: Download the updated version of Moderation Author Notify.