Occasionally there's a piece of software that offers inspiration and a vision of what we can really do with software. The Microsoft Research project WorldWide Telescope offers such software and was officially unveiled for the first time at the TED Conference. You can build your own planetarium in WorldWide Telescope.
According to the project's FAQ, WorldWide Telescope is based on Visual Experience Engine. As you zoom in, higher resolution images is sent over the Internet. To learn more, see Sneak peek at the virtual universe. Coming in Spring 2008 according to the WorldWide Telescope main page.