Stellarium

open source planetarium

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.
It is being used in planetarium projectors. Just set your coordinates and go. Stellarium renders 3D photo-realistic skies in real time with OpenGL. It displays stars, constellations, planets, nebulae and others things like ground, landscape, atmosphere, etc.

Celestia

Open Source Planetarium Tool

Celestia is an application for real-time 3D visualization of space, with a detailed model of the solar system, over 100,000 stars, more than 10,000 galaxies, and an extension mechanism for adding more objects. Celestia allows users to travel through an extensive universe, modeled after reality, at any speed, in any direction and at any time in history. Celestia displays and interacts with objects ranging in scale from small spacecraft to entire galaxies in three dimensions using OpenGL, from perspectives which would not be possible from a classic planetarium or other ground-based display.

Aciqura

Aciqra is a free and open source virtual planetarium and sky mapping program for simulating objects in the sky. It is intended for users who regularly view the sky through a telescope or binoculars, whether visually or with a camera, and need software to help them decide what to view and when.

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GeoGebra

Open source mathematics application

GeoGebra is an interactive geometry, algebra, and calculus application, intended for teachers and students. Most parts of GeoGebra are free software. GeoGebra is written in Java and thus available for multiple platforms. Many parts of GeoGebra have been ported to HTML5 by using the Google Web Toolkit.