"ASPIRE Lab is one of the most innovative and interactive science education websites available on the Internet. You will find not only fun interactive labs, but well designed and produced curriculum content, created by teachers for teachers. The powerful combination of inquiry-based content, along with interactive, hands-on labs provides a powerful visualization tool for you and your students to use. Best of all, the ASPIRE Lab is free!"
I love this site. It has interactive labs and activities, lesson plans, and resources for teachers and students. I use quite a bit of it in my Physics classes. Topics include: tides, atmosphere, lunar phases, Sun angle, seismic waves, scientific method and more.