Behold the Aerogenerator
A British company called Wind Power is developing a new design for mammoth offshore turbines. With two large arms that spin on a vertical axis, the Aerogenerator "mimics the spiraling motion of a sycamore seed." Have a look at the stately thing in (virtual) action below. The tips of the arms, by the way, are 900 feet apart.
The Aerogenerator is expected to be able to power 5,000 to 10,000 homes. Apparently it avoids certain blade weight problems that crop up when you simply try to scale up conventional windmill-style turbines.