The latest version of the free Google Earth has a Sky function. Select "Switch to Sky" in the View pull down menu and Earth will disappear and become a celestial globe. All the commands and layers transform from geographical to celestial, allowing you to search for NGC objects, slew to coordinates, click to display Hubble images, and much more.
I'm still playing around with it, seeing what the various layers do, but the detail is impressive with data from the Digitized Sky Survey and the Sloan Digital Sky Survey.
Post a message here if you find anything cool, odd, or otherwise curious about the new Google
Sky Earth. The only weirdness so far is that the Googlers need to change the scale bar at the bottom left of the window. While the cursor properly shows position in right ascension and declination, the scale bar uses meaningless miles.
We've heard about an upcoming Internet-based sky-charting software very much like Google Earth due to be released later this year from Microsoft, dubbed the World-wide Telescope. I can't wait to see it, but it looks like Google beat them to the punch.