The TortoiseSVN client (Windows) for SVN knows enough about Open Office that when you ask it to diff them, once it's got hold of the necessary versions, it opens Office with both documents open, showing the differences. I use this a lot. I imagine there are even fancier solutions out there, and similar things for Mac/Linux/OS/360 or whatever, but for this very technical user who often feels very untechnical because he wants his lunch, TortoiseSVN (http://tortoisesvn.tigris.org/) delivers.
