STELLARIUM

Website
Astronomy
http://stellarium.sourceforge.net/

"Stellarium is a free open source planetarium for your computer. It shows a realistic sky in 3D, just like what you see with the naked eye, binoculars or a telescope." -Stellarium homepage

This site really sells itself on it's homepage. I've italicized the three points that I find most interesting from an educational perspective. Here are the features, as outlined on the site:

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  • default catalogue of over 600,000 stars
  • extra catalogues with more than 210 million stars
  • asterisms and illustrations of the constellations
  • constellations for eleven different cultures
  • images of nebulae (full Messier catalogue)
  • realistic Milky Way
  • very realistic atmosphere, sunrise and sunset
  • the planets and their satellites

interface

  • a powerful zoom
  • time control
  • multilingual interface
  • fisheye projection for planetarium domes
  • spheric mirror projection for your own low-cost dome
  • all new graphical interface and extensive keyboard control
  • telescope control

visualisation

  • equatorial and azimuthal grids
  • star twinkling
  • shooting stars
  • eclipse simulation
  • skinnable landscapes, now with spheric panorama projection

customisability

  • add your own deep sky objects, landscapes, constellation images, scripts, etc.