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 is application that can run both linux, windows, and Mac Os,  especially in linux stellarium is not defaultly installed, to use and install stellarium on Ubuntu 10.04 is quiet easy just open your synaptic package manager and search using keyword 'stellarium' or go to this page to download source code (tar.gz).
This is some minimal setting and acknowledge start using stellarium : 
Set the right location
Set your location first! The default location is Paris, France (unless someone has re-packaged Stellarium and changed the default).   Press F6 or click on the appropriate icon in the left tool bar to open the Location Window.You can select your location by clicking on the map, by searching for a nearby city, or by entering your longitude, latitude and altitude manually by creating a new location.  One way to determine your precise location anywhere in the world is the Stellarium Location Helper.
Look around
Use the mouse or arrow keys to look around.
Zooming in and zooming out
Use the page up and page down keys to zoom in and out. Zooming on nebulas or planets is very interesting...
Selecting objects
Use the left mouse button to select an object, the right button to deselect the object and middle mouse button or spacebar to center on the selected object.
Controlling time
J slows down or reverses speed, L increases time speed, and K makes time return to normal speed. You can also use the time control buttons in the lower right of the screen.

Play with the view options
Try clicking the buttons in the bottom toolbar, which will appear if you roll the mouse cursor over the status bar at the bottom left of the screen.
Opening the help menu
Press the F1 key for help.
Searching for an object by name
Press F3 to open the search window. You can type in the name of a star, planet, constellation or nebula. As you type a list of matching objects is shown. Pressing TAB selects the next item in the completion list. Press RETURN or click the button in the search window to go to the object.
klik here to see a complate stellarium screenshot.