Here’s a list of even more interfaces for which the documentation has been updated to Firefox 3.1:
Note that a couple of these (notably nsIXPCScriptable) are not very thorough documents, but are up-to-date in that they at least mention all the new stuff, which is covered in roughly the same amount of detail (or lack thereof) as anything else therein.
With these, all of the interfaces already documented on MDC have been updated to cover Firefox 3.1 (as it stands today). There are plenty of interfaces that aren’t documented yet, though. We’ll get to them!