Aciqra, open source virtual planetarium and sky map program. It has the ability to track nearly 120,000 stars, the 8 planets, all 109 Messier object, the sun and the moon from any location on Earth to an accuracy of 1 degree for the next 50 years. It also includes a wealth of built-in tools called "widgets" which include a solar system viewer, an eclipse/transit predictor and a conjunction engine.
The Aciqra project is the world's largest and most active open source GDI-based planetarium available on the internet. This reflects the tremendous amount of energy and the hundreds of hours of work put towards creating and perfecting it.