Can we get energy from the Earth's rotation? Is there any way to harvest large amounts of energy from the Earth's rotation?
 A: This is what tidal power generators do - if earth did not rotate relative to the moon, there would be no lunar tidal motion (there would be a distortion of the earth's equipotential surface but it would not move). Since earth does rotate, you get motion of the oceans. At Fundy Bay, for example, significant power is extracted from this motion. See http://fundyforce.ca/
A: The Foucault pendulum motion is induced via the Earth's rotation.  
Because it moves it can perform work.  
I answer Yes, but irt others it may depend on the more or less flexible definition of vast amount and the size and number of pendulums .
EDIT ADD to 'debunk' myself:  
The above statements are correct,imo, but I will decompose the situation.
Some energy is given to the pendulum to put it in motion and it is only this amount of energy that can be obtained from it. There is no transfer of energy in virtue of the motion of the Earth.  
The pendulum will keep in motion in the same plane in relation to the distant stars, obeying to the 1st Newtons law and keeping the same momentum (under the constriction of maintaining the same distance to the pivot point), summed along the full cycle of forward-backward periodic motion (it is not the instantaneous moment because there is a constant change of potential versus kinetic energy).  
The Earth only transports the pendulum without exerting force on it and without any transmission of energy, in what is called 'parallel transport'. Nevertheless the pendulum is subjected to the normal balanced forces at Earth's surface: inward gravitational force and outward centrifugal one.
So. Lets rewrite the first sentence in a more correct way.
The Foucault pendulum motion is induced via the Earth's rotation.
became
The motion of the Foucault pendulum plane irt the ground is induced via the Earth's rotation. But there is no energy transfer between the object Earth and the pendulum and so it will stop as soon we get back all the energy that was given to it in the initial moment to force its motion.  
Conclusion: It is hopeless the use of the Foucault pendulum to extract energy from the Earth's rotation.  
IMO, it is pedagogic to leave this wrong answer and the correction.  
