A simply fantastic planetarium program that renders realistic skies, in real time. This is hands down the best night sky software that I personally have used to date. It's hard to believe that this is a free program. It runs on OpenGL, and you do need a fairly fast processor.

For: Windows, Linux & MacOSX

A pretty cool program that gives a realistic 3D view of the solar system.... Sun, Planets, Moon, and set them up to where you control the speed of their orbits. Very nice learning tool for all ages.

For: Windows

This program is nice for planning observing sessions. It prints out a calandar sheet for each month telling what phase the moon is in, when it rises and sets, what time it gets dark outside each night, and more.

For: Windows

This is a very nice detailed map of the moon. You can click on an area to find the names of different craters plus information on all of them. The map will show the current moon phase, plus many other features. Highly recommended.

For: Windows

You can download a map of the night sky once a month for free here. The maps are 2 page monthly guides that show what you can see with a telescope, binoculars, or the naked eye. You can also buy atlases, books, posters and many more astronomy related items here.

For: Windows, Mac, Linux & more

This is a GREAT planetarium/deep sky program just loaded with features. It has more than a lot of programs that you pay for, yet it is freeware. It has a steep learning curve, but the payoffs are worth it. Definitely the best free planetarium software out there by a long shot.

For: Windows & Linux

Your computer can help the Search for Extraterrestrial Intelligence. This program works in the background when you are not using your computer, much like a screensaver works. What it does is help the world's largest radio telescope analyze data when you would normally be in a "screensaver" mode. When you start to work again it shuts back down again.

For: Windows & Mac