The Thinkfinity Portal: Learn about and access high-quality, standards-based lesson plans, student activities, reviewed Web sites and other resources for a variety of content areas. For science specifically, click on Science NetLinks on the right hand side of the page.
http://www.thinkfinity.org/
National Science Education Standards (ONLINE)
http://www.nap.edu/html/nses/html/
Benchmarks for Science Literacy (ONLINE)
http://www.project2061.org/publications/bsl/online/bolintro.htm
Science NetLinks is part of the Thinkfinity Network. Thinkfinity partners the AAAS, the National Endowment for the Humanities, the Council of the Great City Schools, the National Council on Economic Education, the National Geographic Society, the National Council of Teachers of Mathematics, and the John F. Kennedy Center for the Performing Arts. Science NetLinks' role is to provide a wealth of resources for K-12 science educators, including lesson plans and reviewed Internet resources.
http://www.sciencenetlinks.com/about.htm
Annenberg Video On Demand (Hundreds of Professional Development Videos accessible for free online!)
http://www.learner.org/view_programs/view.programs.html
The Why Files: Science Behind the Headlines (excellent student-friendly scientific feature articles)
http://whyfiles.org/
NASA for Educators: An Aeronautics and Space Resource for Education
http://education.nasa.gov/home/index.html
Science at NASA: a current online magazine of scientific research, events, and information for students and teachers
http://science.nasa.gov/
Eisenhower National Clearinghouse: ENC's mission is to identify effective curriculum resources, create high-quality professional development materials, and disseminate useful information and products to improve K-12 mathematics and science teaching and learning.
http://www.enc.org/
Powers of Ten: View the Milky Way at 10 million light years from the Earth. Then move through space towards the Earth in successive orders of magnitude until you reach a tall oak tree just outside the buildings of the National High Magnetic Field Laboratory in Tallahassee, Florida. After that, begin to move from the actual size of a leaf into a microscopic world that reveals leaf cell walls, the cell nucleus, chromatin, DNA and finally, into the subatomic universe of electrons and protons.
http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.html
Performance Assessment Links in Science (PALS) is an on-line, standards-based, continually updated resource bank of science performance assessment tasks indexed via the National Science Education Standards (NSES) and various other standards frameworks.
http://pals.sri.com/
RubiStar is a tool to help the teacher who wants to use rubrics but does not have the time to develop them from scratch.
http://rubistar.4teachers.org/
The Science Page-comprehensive links to online science journals
http://sciencepage.org/mags.htm
Science Buddies is a non-profit organization empowering students from all walks of life to help themselves and each other develop a love of science and an understanding of the scientific method.
http://www.sciencebuddies.org/
Mid-continent Regional Educational Laboratory (McREL) is a nonprofit organization created to help educators bridge the gap between research and practice. McRel offers a lesson plans library for science.
http://www.mcrel.org/lesson-plans/science/index.asp
Awesome Library is a web portal to a database owned by the Evaluation and Development Institute. They offer extensive links of interest to science teachers and students.
http://www.awesomelibrary.org/Classroom/Science/Science.html