Last Modified plugin
Kevin of Staggernation just made up a new plugin tag for MT - MTLastModified. MT not only captures the date that you create the entry on (which is editable), it also captures the last date/time when it was modified on.
This may not be helpful to everyone, but If you have a non-traditional use for Movable Type while would be aided in showing how up to date the information is, this would be a really good tag to add into your template.
Here’s the thread where it was discussed on the forums.