The following post offers documentation on the Office 2007 MIME Types that can be used for HTTP content streaming to Office 2007 applications. Due to security measures in both IE and Office 2007, it is important that web sites return Office 2007 content with the correct MIME type header for the type of content returned during a hyperlink navigation.  To see a list of the types and the extensions they map to, see this article post:

Office 2007 File Format MIME Types for HTTP Content Streaming