The Office Migration Planning Manager (OMPM) was released earlier this week. It's a tool that helps folks who are going to manage and upgrade to the latest version of Office (2007). Among other things, it will do a scan of your network to identify Office documents and report back to you on the stats of those documents.
A really cool piece of this is that it will allow you to specify that you want to bulk upgrade the existing binary documents (.doc, .xls, and .ppt) into the new file formats (.docx, .xlsx, and .pptx). This will allow you to take advantage of all the benefits that come with the new formats.