We have something here for whatever science you teach!
All links are organized by category.
ScienceProfOnline.com - Free Biology Education Resource - http://www.scienceprofonline.org/index.html
SPO features completely developed and classroom-tested secondary school and college-level microbiology, cell biology, general biology, and soon anatomy & physiology course materials, including PowerPoint lectures, laboratory exercises, homework assignments, practice test questions, study guides, sample syllabi, as well as a science photos and video library. The site also has a Home School and Classroom Science section for primary school-age children. This part of the site offers fun scientific activity ideas, methods and results of experiments, as well as science coloring pages, word searches, photos and videos.