This extraordinary project, known as Crafting Azeroth, is the work of Minecraft forumite Rumsey, who has been working since February and has created some 275 square kilometers of world. It's "a full-scale reproduction of the World of Warcraft environment" which includes all the caves and dungeons that aren't separate instances. Click through for a download link, but be warned, this one is going to need some hard drive space.
You can get Crafting Azeroth from the Minecraft forums here. Be warned that the 2Gb download extracts to an enormous 24Gb, as that's 68 billion blocks you're squeezing into your PC. While you're waiting for that to happen, you can browse Rumsey's maps and check on the progress of Northrend, Outland, Tol Barad and the Lost Isles, which are forthcoming additions. Impressive stuff, eh?