With this add-in you can permanently remove hidden and collaboration data, such as change tracking and comments, from Word 2003/XP, Excel 2003/XP, and PowerPoint 2003/XP files.
via [Early Adopter Weblog]
Everyone needs this add-in. In the past 6 months, I've received 3 Press Releases with embarassing internal comments and 1 document whose author had gone to significant pains to remain anonymous but who forgot or didn't understand Word's document properties fields.