Microsoft launched WorldWideTelescope, it's downloadable answer to Google Sky, Google Earth and Google Moon, yesterday. Other than being a bit of a memory hog (understandable for the power it provides) and requiring the latest version of DivX and .Net framework to install, WWTelescope is a pretty amazing program. You can aimlessly browse around the solar system and beyond, zooming in with incredible detail on Earth, the moon, other planets or galaxies, or you can download a professional tour of any of the above. Each item you look at comes with various "Imagery" options. You can check out satellite images of Earth, a street view, a hybrid of both or use the incredible cool "Earth at Night" mode. The options for viewing space are too numerous to numerate. For a quick fix, you can browse through various collections of space images, like those taken from the Hubble or Chandra telescopes, and see where in space those images are from.
If anything, WWTelescope is too advanced, offering a slew of advanced and sometimes incomprehensible options aimed at professionals and true hobbyists. You can even hook up your telescope to it. But it's still great, interesting fun for the average user. I just wasted an hour or so "researching" it for this article, and left with the same semi-accomplished feeling I get when I waste time on Wikipedia.
Microsoft products have often fallen behind Google on the coolness factor of their products. This time they definitely have the search giant beat.