Astronomers have found an extrasolar planet that is perfectly positioned to allow a decent analysis of its atmosphere.
Most extra-solar planets are detected because they cause a wobble in their star's motion. This planet, orbiting a sun-like star around 750 light years from Earth, was detected because its orbital plane takes it directly between us and its star.
More: http://www.theregister.co.uk/2006/09/11/transit_planet/