Plugin: Moderate Authors
WordPress allows users to create and save draft posts, which can then be published by a moderator or admin. This process works well for "guest" authors, as well as for controlled environments (like schools) where all content must be reviewed and approved. An interesting quirk, though, is that once the item is published, the original author can comment on it without restriction, regardless of any comment moderation settings that might be in effect.
Moderate Authors is a WordPress 2.0 plugin I wrote to remedy this situation. When activated, the author of any post is forced through the moderation queue. The only exceptions are authors with the "edit options" capability, who I consider to be administrators and therefore exempt from comment moderation.