Just in time for Firefox 1.5, the XPCOM Reference and Object Reference have been updated. It includes all of the new interfaces and components available in Mozilla 1.8. Likewise, those interfaces that are no longer available have been removed.
The index page has been altered so that more categories are available, hopefully so that finding particular interfaces is easier, or perhaps harder. Note that the search isn't up to date yet so that method of finding things may not work well. In addition, most but not all interfaces are marked as to whether they are expected to be used as a service.