ArXiv. org — open access to millions of e-prints in physics, math, comp. sci., quantitative biology, quantitative finance and statistics, electrical engineering and more. Funded by Cornell U.
ATETV (Advanced Technological Education TV) — funded in part by the NSF (National Science Foundation), ATETV showcases ATE disciplines, including info tech, engineering, agricultural tech, process tech and rapid prototyping/manufacturing. New videos uploaded weekly
Automobile Fuel Economy — find out greenhouse gas emissions and fuel economy for your car, tips on improving gas mileage, gasoline prices across the nation and more
Biodiversity Heritage Library — providing access to over 40k journals and books – legacy literature – on biodiversity: botany, zoology, natural history, evolution, classification, paleontology and more. Int’l in scope and historical in coverage (from 1450 to present)
Charles Darwin’s Library — digital edition and reconstruction of the surviving books owned by Darwin. Includes his notations and markings
Codeacademy — learn to code interactively for free
Darwin Online — from complete publications of Charles Darwin [Origin of Species, Voyage of the Beagle, Descent of Man], private papers and manuscripts, to reviews and responses, Darwin’s specimens, obituaries and more
DOAJ: Directory of Open Access Journals — free, full text, quality controlled scientific and scholarly journals, covering numerous subjects and available in many languages
Einstein Light — Einstein’s theory of relativity explained through animation and simple text
Energy in Brief — by the EIA, Energy Information Administration. What everyone should know about energy. Fact sheets and articles that explain important energy topics in plain language for the layperson or non-specialist
EOL – Encyclopedia of Life — an open-access, collaborative encyclopedia whose vision is “global access to knowledge about life on Earth.” A convenient, info-rich resource for researching everything about organisms
EPA.gov — official website of the Environmental Protection Agency
Food Insight — your nutrition and food safety resource. By the IFIC: International Food Information Council Foundation
Futurity.org — news from leading research universities
Khan Academy — thousands of videos and interactive exercises for learning math, science, computer programming, history, art history, economics and more
Linus Pauling Online — research site dedicated to Nobel-winning American chemist. By Oregon State U.
The Naked Scientists — by University of Cambridge. Science news, interviews, articles, podcasts and more
NanoHUB — simulation, education & community for nanotechnology
Nanotechnology Portal — by NIST, the Nat’l Institute of Standards and Technology. Covering such subjects as nanobiotechnology, nanoelectronics, nanofluidics, nanomechanics, nanophysics and more
Physics for the 21st Century — explore the frontiers of physics research with the scientists on the front lines in this 11-unit course in modern physics for high school physics teachers, undergraduate students, and science enthusiasts
Phys.org — top news in science and technology: nanotechnology, physics, space & earth, electronics, chemistry, biology, medicine & health and more
Resources for the Future — independent research – rooted primarily in economics and other social sciences – on environmental, energy, natural resource and environmental health issues
RenewableEnergyWorld.com — World’s #1 Renewable Energy Network for News, Information & Companies
SageMath.org — a free open-source mathematics software system licensed under the GPL. It builds on top of many existing open-source packages: NumPy, SciPy, matplotlib, Sympy, Maxima, GAP, FLINT, R and many more
Science in Action — by the BBC. “A magazine program pulling together the science issues of the week and delivering breaking science news from the just-released journals.”
Science.gov — gateway to millions of pages of authoritative federal science info provided by U.S. govt. agencies, including R & D results
ScienceBlogs.com — access to more than 70 blogs by selected leading bloggers from a variety of scientific disciplines
ScienceDaily — latest news and articles in science, health, environment and technology
STEM Career — for those seeking and promoting careers in Science, Technology, Engineering & Math
TestTube — behind the scenes videos in the world of science
World Library of Science — connecting the world scientific community with educators and students and offering science education resources at no cost
WorldWideScience.org — global science gateway to federated searching of national and international scientific databases and portals. Results provided in multiple languages