For some time now, the Office applications have allowed you to define document properties: extra information (or metadata) that can be carried around with the document itself.  If you're using a SharePoint server those properties can be promoted to be visible in a SharePoint library.

For me, the problem has always been that those properties are hidden away.  It's a case of "out of sight, out of mind".  I think a lot of people could make good use of them, if they simply remembered to use them.

The 2007 versions of Word, Excel and Powerpoint have a new way to visualise these document properties, called the Document Information Panel.  In essence, it's a small InfoPath form that appears at the top of the application window, just below the Ribbon.  It puts the document properties "in your face" so they're impossible to ignore.  If you're working with a SharePoint server, you can configure which properties are "required" and the user is unable to save the document to SharePoint without first supplying values for all required fields.  Also, since the Document Information Panel is just an InfoPath form, you can supply customised forms to be used with documents that are held in specific SharePoint libraries (or correspond to specific Content Types).  These customised forms can be used for branding, and to include instructions/reminders for users.