Science Kids has an experiments section full of hands-on experiments that represent a great way to learn more about science.
http://science.howstuffworks.com/
Huge resource for science information across a range of topics on the How Stuff works website. The top level categories are Earth Science, Engineering, Everyday Science, Life Science, Military, Physical Science, Space Science, and Supernatural Science. There are many sub categories beneath each of those. Primarily at an adult level, but useful as a teaching resource as it contains hundreds of articles, images, and videos.
http://www.all-science-fair-projects.com/
Search or browse over 500 ideas for projects for every science topic, from Astronomy to Zoology.
http://www.super-science-fair-projects.com/
Contains ideas, experiment guidelines, as well as information on planning, researching, writing a report, and displaying a science fair project. Suitable for Years 1 to 13.
http://www.sciencealive.co.nz/
The Science Alive centre is based in Christchurch but the website contains a lot of online information for both students and teachers (see the Education section). Information on various science fairs and competitions is listed as well as the various exhibits.
http://www.sciencebuddies.org/science-fair-projects/science-fairs.shtml
Lots of online resources for students, teachers, and parents involved in science fairs.
