NASA - The National Aeronautics and Space Administration maintains a wealth of information on astronomy and space exploration.  This information is actually spread over dozens of sites and includes NASA TV, multimedia, stunning photos and activities for children of all ages. It's a huge collection of information, so you might have to do several seaches to find what you want.

Space.com - This is a great way to keep up with space in the news. This is a commercial website with lots of content, but it is very well organized, and some of their slide shows are just outstanding!

Biology at About.com - About.com has a wealth of information written by outstanding teachers and/or experts in their field that provide lots of information for students and those who are just interested in the subject.  This, along with several other About.com sites are given here just because they are so good!

Chemistry at About.com - This site covers the fundamentals of chemistry and is certainly worth checking out if you are just getting started.  There are also some excellent experiments.

Physics at About.com - This is another of the About.com educational sites that presents an excellent overview of the subject.  There are also some pretty neat experiments here as well.

Physics Lecture Demonstrations from the Departament of Physics of University of California at Berkeley - this is a collection of physics experiments designed for teachers, but since they use simple equipment, many are also suitable for advanced students and experimenters.

Geology at About.com - Another of the About.com sites.

USGS - The United State Geological Survey is the U.S. government agency responsible for the study of all things related to geology.  Just as with NAS above, and NOAA below, there is a wealth of information, and your biggest challenge may simply be to find what you need.  But the search is half the fun!

Weather at About.com - What can we say other than some of the best teachers have collected some of the best information?

NOAA - Otherwise known as the National Oceanograhic and Atmospheric Administration, this is the agency responsible for public weather forecasting in the United States.  NOAA has many sites nationwide with a lot of material for both students and teachers, and this is the starting point for all that information.  Start by clicking on "NOAA Education."

Some Simple Electricity Experiments - These are from the "The Exploratorium Science Snacks" website.

Lessons in Electric Circuits - This site contains a complete textbook covering basic electricity and electronics.  It is probably geared more toward older students.

Electronics For Kids - A nice collection of simple electronics experiments.

The American Radio Relay League - If you are interested in electronics as a hobby, you can't do better that amateur radio.  And the best place to learn about amateur radio in the U.S. is the ARRL website.

The TEARA Volunteer Examiner Team - In the U.S., amateur radio exams are administered by accredited volunteer examiner teams. One such team, located in eastern North Carolina, has a great website with additional amateur radio resources.  Click on the "Resources" link.

Electronics Tutorials - Here you will find a series of lessons on electricity and electronics that are geared toward preparing for for an amateur radio license.   The theory portion is applicable everywhere.

How Stuff Works - This is the absolute best site for anyone who wants to know how the items we use everyday works.  Browse and learn!

Just Learn Morse Code - Go to this link to get a free Morse code trainer that teaches you to receive Morse code by sound.  If you learn to receive it, you will have no problem sending it!

WD8LQB Learning Morse Code Podcast Podcasts - This series of free podcasts will take you through learning the code step by step!

Morse Cat - Another good free Morse code trainer is found on this site.  This one features a kitty cat doing the sending!   The author's site is in German by default, but this link will take you to an English version.

G4FON Trainer - This free Morse code trainer will teach you how to receive Morse code via radio under realistic conditions.  Use one of the trainers to above to learn the code, and then "graduate" to this one.

WinMorse 2 - A free program that converts typed text into Morse code is available on this site.  It won't really help you learn all that much, but it will help you hear what the code is supposed to sound like.

SuperAldis - The free program on this site teaches you how to receive Morse code by flashing light.

Flags - The free program on this site will train you to recognize nautical flags once you have memorized them.

Semaphore flags information - This Boy Scout site has lots of great information for anyone who wants to learn Semaphore signaling.

School Science Lessons - Queensland College - This site contains a wealth of experiments based on the 1979 edition of the "New UNESCO Source Book for Science Teaching."  For many years, this material has provided teachers and experimenters with instructions on how to make science equiment from common items.

UNESCO Guidebooks - This site, maintained by "International Council of Associations for Science Education" contains an archive of the UNESCO guidebooks on its old site.  Much of the content of the "School Science Lessons" site comed from these guides.  You can still download these guides in .pdf form, but since ICASE has moved to a new site,this link could go away at any time.  If you are a teacher or serious hobbyist, I strongly urge you to download this information while you can.

UNESCO Handbook - A pdf scan of the 1973 "New UNESCO Source Book for Science Teaching." is available here. This book contains much of the information found on the previous two sites, and is an excellent resource for the student or experimenter.

Science Paper Models - This site allows you to print out a variety of science related models and to then cut and glue them together.  Check out the sundial, globe and dinosaurs!  And if you enjoy this sort of thing, be sure to plug "paper models" into your favorite search engine.  There are tons of free paper models online.

The Sciece Toymaker Page - quite a few neat projects, and most are very simple. I wish I'd thought of some of these.  Check it out!