http://www.newscientist.com/news/news.jsp?id=ns99993232 The speed of gravity is experimentally determined to be the same as the speed of light, meaning that “if the Sun suddenly disappeared from the centre of the Solar System, the Earth would remain in orbit for about 8.3 minutes—the time it takes light to travel from the Sun to the Earth. Then, suddenly feeling no gravity, Earth would shoot off into space in a straight line.”
Update: Nature has the same story, but told more professionally. (I don’t like New Scientist much.) The second paragraph states that the measurement is only approximate (as opposed to the third-from-last), and it also tells in more detail how the measurement was made. There’s no equivalent of NS’s nice Earth- shooting- into- space visual image though. 14:42