Giver - Open Source File Sharing Tool

Giver is a simple file sharing desktop application. Other people running Giver on your network are automatically discovered and you can send files to them by simply dragging the files to their photo or icon shown in Giver. There is no knowledge or set up needed beyond what the person looks like or their name to use Giver.

Lanshark - Open Source LAN Filesharing Tool

Lanshark is a free filesharing tool for local area networks. Lanshark allows you to share files with other users in the same network more efficiently. It automatically detects other lanshark users in the same Network and lets you browse trough their shares. Lanshark has a very fast search function that allows you to search through all the shares in the whole network in just a few seconds!

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.

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.