[Update]: The newest update has brought in the legendary Gates of Ahn'Qiraj event and two accompanying raids!
Besides the corrupted blood plague that hits a bit too close to home these days, the opening of the Gates of Ahn’Qiraj is very likely World of Warcraft's most memorable in-game event. Not only did it require the coordination of an entire server in order to launch the grand invasion, but the sheer scale of the battle at the gates themselves was so massive that not even the beefiest of servers could truly cope with it.
So if you weren't around when this happened, or if you simply managed to miss it, I'm very happy to say that you'll soon have another chance to experience its lag-filled majesty! According to Blizzard's latest announcement, the Gates of Ahn’Qiraj event and its accompanying content will become available on July 28th across all realms.
Once it arrives, players will be able to start the incredibly lengthy quest chain to craft a Scepter of the Shifting Sands that rewards the highly prestigious Qiraji mount. The whole server will also need to start turning in gathered resources to advance the Ahn’Qiraj war effort, as without supplying the army and launching the invasion, the Gates of Ahn’Qiraj will remain firmly closed and the two raids unavailable.
That's pretty much everything you need to know, so look up what resources you'll have to turn in, and start preparing for the mad rush on July 28th. Have fun, and good luck with the opening event!