Out west there are lots of "wind farms". These huge windmills turn the energy of the wind into 60 cycle AC current by means of an induction generator. I can't decide if they look cool or look like a blight on the landscape. A little bit of both, I guess.
The towers are 100 to 300 ft tall. The blades anywhere from 60-130ft long. If they had legs they could be Tripods from War of the Worlds.
I couldn't find info on how big the generator housing was but think medium sized moving van.
The blade tips are moving at around 300ft/sec when they're rotating at 22 rotations per minute.
They can produce between 100kw up to megawatts to be sold to utilities.
The blades adjust to the wind direction to prevent the torque from twisting them off. There have been incidences of the winds spinning the blades so fast they disintegrate.
This video shows a three blade Danish wind turbine disintegrating.
I got quite a bit of my info from Wikipedia http://en.wikipedia.org/wiki/Wind_turbine