Things finally seem to be settling down as we're back to the normal maintenance routine of downtime between 5am and 7am CEST. Of course, our poor American brethren were once again in guinea pig mode. They experienced a rather lengthy period of extended maintenance yesterday afternoon so, as usual, don't hold your breath.
As if anticipating the whiff of downtime, Daniel W. compiled a rather extensive list of things do to during the (hopefully short) downtime. See y'all when the servers come back up!
Update: All the servers seem to be back up a bit earlier than anticipated. However Blizzard have posted a note concerning 'technical difficulties' relating to the login/authentication servers and promise they're looking into it. Hopefully the problem will be fixed pretty quickly but if you find yourself unable to get into Azeroth, that's why. All you can do is keep calm and carry on, folks.