The saga of the Rampage and Shadowburn (US) battlegroups continues. All realms in those battlegroups have been down since at least 11:00 AM EDT this morning. Blizzard says they're working on it, but so far all we've seen is an ETA given, which was promptly missed -- that ETA was 1:30 EDT. The new word is to expect an update roughly now; I'll be keeping my eye on it and will update this post if there's any news.
Once again, the affected US realms are Agamaggan, Alexstrasza, Alleria, Azshara, Baelgun, Balnazzar, Blackhand, Cho'gall, Dark Iron, Destromath, Dethecus, Detheroc, Emerald Dream, Garona, Gorgonnash, Greymane, Gul'dan, Hellscream, Illidan, Kael'thas, Kalecgos, Kirin Tor, Lightninghoof, Maelstrom, Malfurion, Moonrunner, Nazjatar, Ravencrest, Sargeras, Spinebreaker, Staghelm, Stormreaver, Twisting Nether, Ursin, Whisperwind, and Wildhammer.
Zul'Jin is also reportedly down, as well as Burning Legion and Lothar; I'm unsure of the status of the rest of the Ruin and Vindication battlegroups.
Update: It looks like Ruin and Vindication are down in their entirety. Meanwhile, Blizzard updated to let us know they're still working on it, and they expect the Rampage and Shadowburn realms to be up by around 1 PM PDT/4 PM EDT.
Update 2: Apparently the Ruin and Vindication issues are a hardware problem; Blizzard knows about it and expects to have those realms back up by 3 PM PDT/7 PM EDT.