Math:
MathNerds provides free, discovery-based, mathematical guidance via an international, volunteer network of mathematicians.
Math for America includes online resources for lesson plans, activities, and demonstrations that are consistent with the best practices in mathematics education.
GeoGebra is a multi-platform, free, dynamic mathematics software for all levels of education that brings together geometry, algebra, spreadsheets, graphing.
American Mathematics Competition is a national contest managed by The Mathematical Association of America.
General Science:
PBS Science & Technology Teacher Resources provides K-12 lesson plans and activities based on PBS programs including NOVA.
Science Learning Network includes inquiry-based resources from an international network of science museums.
Discovery Education provides engaging digital resources to schools and homes with the goal of making educators more effective, increasing student achievement, and connecting classrooms and families to a world of learning.
Science NetLinks Providing a wealth of resources for K-12 science educators, Science NetLinks is your guide to meaningful standards-based Internet experiences for students.
Scirus is a comprehensive science-specific internet search engine covering over 167 million science-specific web pages. This free tool is maintained by Elsevier, Inc.
Pennsylvania Science Olympiad provides useful information for participants, coaches, organizers, and followers of the state's Science Olympiad competition.
Biology:
The Biology Corner is a teacher-created site with a large amount of worksheets, activities, and lesson plans.
Classroom Resources from the Koshland Science Museum contain materials for virtual field trips and supplemental lessons that focus on infectious diseases and DNA.
Virtual Frog Dissection is a free, virtual dissection of a Grass Frog that highlights dissection technique and major organs.
Chemistry:
LabWrite is an interactive online guide that directs students through the entire laboratory experience – includes sections for lab instructors and professors.
ChemBioFinder is a scientific database offering basic information, including physical property data and 2D chemical structures for several thousand most common chemical compounds.
WebElements is an interactive online periodic table including basic information and properties.
ChemMatters magazine for high school chemistry includes Teacher’s guides, background information, follow-up activities, classroom demonstrations and other teaching resources.
Earth & Space Science:
Google Earth lets you fly anywhere on Earth to view satellite imagery, maps, terrain, 3D buildings and even explore galaxies in the Sky.
EarthNet is a virtual resource center for Earth Science Educators
Skyview Café is an interactive planetarium that allows users to explore astronomical information both graphically and numerically.
Windows to the Universe Windows to the Universe is an extensive astronomical learning system covering the Earth and Space sciences for elementary and secondary levels in English and Spanish.
Educational Resources from the Pennsylvania Geological Survey.
Physics & Physical Science:
Fear of Physics is an interactive, visual, and easy-to-use site that shows some laws of physics in action.
The Physics Classroom Tutorial is an online physics tutorial written for high school physics students. The tutorial was originally developed for physics students at Glenbrook South High School in Glenview, Illinois.
Hyperphysics contains online tutorials that cover a wide range of physics topics, including modern physics and astronomy. Material is organized through extensive concept maps.
Physics Education Technology (PhET) is an ongoing project to develop simulations and lessons for teaching and learning physics and chemistry.
Physlets are Physics Applets that explain a wide variety of physics concepts.
Environmental Science:
Center for Environmental Education works with K-12 schools to address climate change issues and to cultivate healthy lifestyles.
Environmental Education and Training Partnership offers educators information, resources, and links for promoting academic achievement and environmental literacy.
Global Warming Activities selected by master teachers as follow-up activities to reinforce the concepts learned during a visit to the Koshland Science Museum or a Virtual Field Trip.
Pennsylvania Envirothon is the state-level of a national environmental competition; the site includes competition details, teacher resources and sample station questions.
Council for Environmental Education houses curricular materials for Project Wet, Project Wild, Flying Wild and Wet in the City programs.
Math:
The Center for Mathematics Education contains curricula, multimedia activities, and professional development for elementary and secondary mathematics educators.
TERC mathematics and science education resources include research, curriculum and technology development, and implementation support in the form of professional development and assistance to districts and schools.
Geogebra - a free multi-platform mathematics software that adds interactive aspects to math visualizations.
Math Forum is a leading center for mathematics and mathematics education on the Internet. The Math Forum's mission is to provide resources, materials, activities, person-to-person interactions, and educational products and services that enrich and support teaching and learning in an increasingly technological world. And they have a great directory of links to relevant resources.
General Science:
Smithsonian Science Education Resource Center - Founded by the Smithsonian and National Academies, SSERS (formerly NSRC) is an intermediary organization that bridges research on how children learn with best practices for the classroom.
Department of Energy's Education Toolbox - Provides lesson plans and information on age-grade and subject matter resources for "energy" to help point students along the path of learning.
The Center for Innovation in Engineering and Science Education contains interdisciplinary projects that teachers throughout the world can use to enhance their curriculum including projects that utilize real time data available from the Internet, and collaborative projects that utilize the Internet's potential to reach peers and experts around the world.
The National Science Digital Library contains K-12 teaching resources in a variety of science disciplines as well as professional development tools. Very nice searching and filtering of their extensive collection.
Biology:
Access Excellence contains Health and Bioscience resources for teachers and learners from The National Health Museum.
Action Bioscience is an education resource from the American Institute of Biological Sciences.
BIODIDAC is a bank of digital resources and images for teaching biology.
BioInteractive contains free educational resources from the Howard Hughes Medical Institute including a variety of virtual labs.
Biotechnology Curriculum Framework is a collection of biotechnology lessons that incorporate science, technology and agriculture education objectives supported by the Pennsylvania Department of Education.
Enlivening Genetics Education is a collection of interactive Flash tutorials that investigate concepts including Mendelian genetics, protein synthesis, inheritance patterns and natural selection.
Chemistry:
The ChemCollective is a collection of virtual labs, scenario-based learning activities, and concepts tests which can be incorporated into a variety of teaching approaches as pre-labs, alternatives to textbook homework, and in-class activities for individuals or teams.
ChemEd DL The Chemical Education Digital Library consists of collections of digital materials intended for teaching and learning chemistry.
General Chemistry Online contains resources for students and teachers of introductory chemistry including tutorials, glossaries, and simulations.
Earth & Space Science:
SEGway (Science Education Gateway) contains K-12 lessons designed by teachers and scientists in the areas of Space Science, Sun-Earth, and Solar System.
NASA For Educators contains learning and teaching resources for K-12 students and teachers in astronomy, physical sciences, technology and other areas.
NOAA Education contains resources for students and teachers in topics including weather, climate change, ocean and space science.
USGS Education provides scientific information intended to help educate the public about natural resources, natural hazards, geospatial data, and issues that affect our quality of life. Discover selected online resources, including lessons, data, maps, and more, to support teaching, learning, education (K-12), and university-level inquiry and research.
Enduring Resources for Earth Science Education - Promoting, creating and publishing this site occurs through a collaboration between middle and high school teachers and Earth scientists.
Physics & Physical Science:
The comPADRE Collections a free, web-based database of teaching and learning resources for K-20 Physics, Astronomy physical sciences, and is part of the NDSL.
NASA Office of Education contains learning and teaching resources for K-12 students and teachers in astronomy, physical sciences, technology and other areas.
The Physics Front is a web-based area for teachers of Conceptual, AP and Algebra-based physics as well as teachers of Physics First and Physical Science. The resources contained are meant to enrich the high school physics experience.
Environmental Science:
EPA for Students and Educators provides resources and services focused on lesson plans and activities, grants and awards, and student resource pages.
EELinked includes resources for professional development, climate change, global warming, lesson plans, endangered species, national and international events as well as hosting a newsletter and job listings. North American Assn for Environmental Education.
The Pennsylvania Dept of Education Environment and Ecology Education Website includes lesson plans and other teacher resources including program correlations for Project Wet and Project Wild.
