In my old college job, I started in the MIT department with a boss who did everything in Excel. Though marvellous within the app, I can vouch the data isn't the easiest to reuse, it does involve hair-pulling. Sometimes feels like tooth-pulling.
But Mark Nottingham's found a cunning way of "globalizing" Excel data for reuse, borrowing the tricks of XHTML microformats: Adding Semantics to Excel with Microformats and GRDDL. He's turning it into RDF, but the technique is more generic (bleah, who cares… "Excel as RDF editor, here we come!").
Looks very handy. Hmm, I wonder whether the extraction could be automated/made two-way through Apache POI..?
See also: Using OpenOffice Draw to author RDF[Danny]