"Dedicated to providing high quality, instructional, free math videos to middle school, high school, and college students who need math help"--videos are created by K-12 teachers and college professors.
BEN (BioSciEdNet): A Digital Library of the Biological Sciences for Biology Teaching
A portal for online collections of biology education resources maintained by the American Association for the Advancement of Science (AAAS). Requires free registration.
BioEd Online: Biology Teacher Resources
This site from Baylor College of Medicine "utilizes state-of-the-art technology to give you instant access to reliable, cutting-edge information and educational tools for biology and related subjects". Includes presentations, slide sets, classroom activities, and teacher resources.
Biology Project (U. of Arizona)
An online, interactive resource for learning biology. Includes lesson plans and activities by high school teachers.
ChemCollective (Carnegie Mellon)
Online resources for teaching and learning chemistry. "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."
Climate.gov: Educational Resources (National Oceanic and Atmospheric Administration)
Includes teaching resources, professional development opportunities, and multimedia
"A free and open learning community for sharing newer and emerging tools to teach science (real-time data collection, simulations, inquiry based lessons, interactive web lessons, micro-worlds, and imaging)."
National Institute of Environmental Health Sciences (curricular materials and lesson resources)
Office of Science Education (National Institute of Health)
Resources organized by topic and grade level plus lesson plans.
The Periodic Videos (U. of Nottingham)
Short videos on each element
". . . provides a wealth of standards-based resources for K-12 science educators, including lesson plans, interactives and reviewed Internet resources.