NASA and Google have signed an agreement to "work together on a variety of challenging technical problems ranging from large-scale data management and massively distributed computing, to human-computer interfaces".
NASA will provide Google with interesting data, like statistical data on atmosphere, that will be available in Google Earth. Other plans include: "real-time weather visualization and forecasting, high-resolution 3-D maps of the moon and Mars, real-time tracking of the International Space Station and the space shuttle. This agreement between NASA and Google will soon allow every American to experience a virtual flight over the surface of the moon or through the canyons of Mars."
The collaboration makes perfect sense: NASA has a lot of collected data, Google has a scalable system that lets it share the data with the world.