Hex Lands is a new world generator mod that generates biomes in hexagon shapes similar to the board game Settlers of Catan.
The layout of each biome allows for a whole new way to play the game and can even make multiplayer servers more dynamic. The biomes are also generated at random heights so each border can lead to a potentially steep drop or very high cliff.
But other than the shape of each biome, the world should function as any other standard Minecraft world. Structures and mobs will generate naturally including villages that may even bleed over to adjacent hexes.
And you can even set the config to generate hexes in the Nether as well!