That's already there. On the topic lists page (the one that shows all the subjects), there's a little arrow just to the left of the subject that'll jump you to the first post you haven't yet read. If you open a message with using it, within a message topic, there's a "View First Unread" link at the upper, left corner of the messages.
-jk
Indeed it is... (just not where I'm used to finding it..) Thanks.