The newest technique for discovering extrasolar planets: Transit Timing Variation

Two weeks ago the discovery of a new planet fifteen times the mass of the Earth was discovered called WASP-3-c, a planet that is more interesting not in and of itself but in the way it was discovered, a method called Transit Timing Variation that relies on watching the wobbling of planets orbiting a star, instead of the star itself. By watching the movement of a planet around its star and the slight variations each time it passes in front, it is possible to tell whether it is also being tugged on by another planet orbiting in the same system. Considering how much less massive planets are than the stars they orbit, this method makes it possible to detect planets of a very small mass, including that of the Earth.

For articles on this in English see here and here, and if you prefer you can read about it here auf Deutsch or here на български.