World of Warcraft has been recreated in Minecraft by an extremely diligent and creative gamer named Rumsey. The project, named "Crafting Azeroth" has been in development for a while and is a "a full-scale reproduction of the World of Warcraft environment." It spans 275 square kilometers and contains over 68 billion (with a B) blocks. To date, all of Eastern Kingdoms and Kalimdor are about done, and work has now started on the Outland and Northrend continents from the WoW expansions.
In order to help with the heavy lifting, Rumsey created custom software that converts the continents of WoW in to Minecraft blocks. The project is simply breathtaking, and you if you want to explore it yourself, you can download the map for free. However, since it's such a massive project, be aware that the files are around 24 GB; you'd better make sure you have a lot of harddrive space before downloading.
If you want to learn more about Crafting Azeroth or download the amazing map, check out the Minecraft forums.