Over on our sister blog Crave, we post about the occasional for amateur astronomers. But if you aren't willing to shell out the cash for a pricey telescope, night sky projector, or home planetarium, never fear--that's where the wonderful world of free webware comes in. Wikisky was described by the Wired Science blog as "Google Earth for space," which is essentially an apt description. You can use Wikisky (which isn't actually a wiki, for the record) to view and navigate the entire night sky either as a graphical representation, or in legit photographs courtesy of the Sloan Digital Sky Survey.
The interface isn't as easy to get the hang of as Google Maps or Google Earth's, but then again, I don't think very many of us are as familiar with the night sky as we are with a world atlas. It also was a bit slow to load, even in the graphical form, and it is more difficult to zoom in and out because Google Maps' quick keyboard commands don't apply.
This appears to be very much a project in the works--currently, only a quarter of the night sky is available--but I think it's ultimately a great idea. If Wikisky can keep growing and adding more functionality, I can see this being an awesome information resource, and an even awesomer time-waster.