Check out Scholastic's collections of science experiments for grades 3-5 and grades K-8 from Scholastic.
When you need new ideas to boost your science curriculum, CanTeach offers a great collection of links to online resources that will meet the needs of any science unit.
Bill Nye is the great “Go-To” when it comes to science. He hasn't let us down yet. So head to Bill Nye, The Science Guy for great resources to use in your science units.
The Exploratorium has put together a huge list of easy experiments you can do at home or in the classroom. Go ahead and give it a try.
The Science Spot has a great lesson on how to use the Scientific Method. This lesson is complete with recording ideas, safety precautions and using the scientific method while doing an actual experiment. Really helpful for new science teachers, but those of us who have been teaching a few years will love it too.
The Washington State LASER site has an extensive how-to on Science Notebooks in the classroom.
Planting Science is another site with information on using Lab Notebooks and Science Notebooks in the classroom.
It can sometimes be difficult to find meaningful science experiments for younger students. For teachers of grades K-4, 100 Fun Science Experiments offers illustrated STEM projects for your classroom, organized by age or topic.