Yesterday, NASA announced that Kepler has found 11 planetary systems with a total of 26 new planets.  This triples the number of stars known to have multiple planets in orbit.  

Additionally, each of these new planetary systems contains between two and five planets with close enough orbits that the gravitational interaction between the planets accelerate their orbits.  This acceleration changes the orbital periods of the planets, which allows astronomers working with Kepler a new way to verify the existence of these planetary systems (check the link for a video explaining this).