This site has explanations and activities for 50 common science questions. Many with diagrams and photographs. There are also photos from the Hubble space telescope and links to other astronomy sites. The Bill Nye website is worthy of mention because it is designed with the young students' interests in mind.
Activities generally require simple materials that are common household items.
There is a section dedicated to lesson plans and science suggestions. There s something for everyone at this site. This website is cool because it is very useful for both teachers and students. There are great lesson plan ideas as well as cool activity suggestions. This is a good website for researching any subject.