Is there any anti-gravity material? I want to know if there is any anti-gravity material. I am thinking of making flying vehicles which are made up of anti-gravity material so that they will not experience any gravity on them and can easily take off and be more fuel efficient. Is there any such thing? Or any workaround?
 A: A from a theoretical physics point of view not completely off the mark approach to anti-gravity effects comes from certain versions of supergravity described in wikipedia, which is a unified supersymmetric point-particle quantum field theory.
Some particular versions of this theory not only contain the "usual" atractive graviton, a spin-2 particle, but in addition a so-called graviphoton is predicted (1). This graviphoton is a spin-1 vector field, interacts with mattar at the normal gravitational strength, and behaves generally like a massive photon. The fun thing about it is that it can give rise to attractive and repulsive forces. The repulsive forces feature can in principle give rise to anti-gravity effects, however the real-world / everyday usefulness of this has not yet been tested ... ;-)
For more see this blog article on Uduality (2).
References:
(1) A model for a light graviphoton, R. Barbiery and S. Cecotti, Zeitschrift für Physik C Particles and Fields, 33(2), 1986, 255-261
(2) Antigravity from Supergravity, Physics blog post on: U.Duality thoughts on the new mathematics and physics, posted 24. November 2012
A: In the spirit of conspiracies and dubious theories, take a look at the so called Biefeld Brown effect.Some have claimed that Penney's 1965 paper as a possible source of rationalizing their beliefs. I don't know enough to offer an opinion either way. However, Mythbusters et al have obtained negative results in all their experiments.Take it for what its worth.
A: Forget anti-gravity material. As far as we know, there is none--gravity is always an attractive force. But there is a workaround: Use something with the appropriate properties, i.e. something that does have repelling force. Electromagnetism! All you need to do is separate enough charge, say a few grams of electrons, place half of them at the airport and attach the other half to your flying machine. Off they go with a mighty force that can lift Mount-Everest sized objects to the moon. Simple as that. (Calculation of the force between two 1g clouds of electrons left as an exercise--it's immense!).
Of course, the hard part is getting at a gram of electrons (without any positive charge nearby).
A: When you say "anti-gravity material", the closest thing I can think of is the hypothetical concept of negative mass:

In theoretical physics, negative mass is a hypothetical concept of
  matter whose mass is of opposite sign to the mass of the normal
  matter. Such matter would violate one or more energy conditions and
  show some strange properties such as being repelled rather than
  attracted by gravity. It is used in certain speculative theories, such
  as on the construction of wormholes. The closest known real
  representative of such exotic matter is a region of pseudo-negative
  pressure density produced by the Casimir effect.

But it gets more complicated because there are actually three different kinds of mass: gravitational mass, passive grativational mass, and inertial mass:

Thus objects with negative passive gravitational mass, but with
  positive inertial mass, would be expected to be repelled by positive
  active masses, and attracted to negative active masses. However, any
  difference between inertial and gravitational mass would violate the
  equivalence principle of general relativity. For an object where both
  the inertial and gravitational masses were negative and equal, we
  could cancel out mi and mp from the equation, and conclude that its
  acceleration a in the gravitational field from a body with positive
  active gravitational mass (say, the planet Earth) would be no
  different from the acceleration of an object with positive passive
  gravitational and inertial mass (so a small negative mass object would
  fall towards the Earth at the same rate as any other object).

In any case, there does not exist any such thing, to the extent of human knowledge.
A: Anti-gravity is impossible, as it would let you build a perpetual motion system, as follows.
Assume we have a system in which we can capture the kinetic energy of a falling mass. For example, a ball that falls onto a scooped wheel to drive it. Take the ball and move a sheet of anti-grav material under it. As the ball now no longer feels the earth's gravity, we can push it up above the wheel without using any energy. Now remove the anti-grav sheet. The ball will fall onto the wheel and thus generate energy.
This violates the law of conservation of energy, i.e. the first law of thermodynamics. Hence it is impossible, and hence anti-gavity cannot exist.
