Brilliant (https://brilliant.org/) Learning math and science through problem solving
Foundational Questions Institute (https://fqxi.org/)
Science Research (http://www.scienceresearch.com/scienceresearch/)
Sci-News (http://www.sci-news.com/)
Catalogue of Anomalies, by subject (http://www.science-frontiers.com/catalog.htm)
Union of Concerned Scientists (http://www.ucsusa.org/)
Science Daily (http://www.sciencedaily.com/)
The Edge (http://www.edge.org/)
Science Online (http://www.scitechdaily.com/)
arXiv (http://www.arxiv.org/)
Scientific American Discussion Board (http://science-community.sciam.com/category/Discussions/3)
The Internet Encyclopedia of Science (http://www.daviddarling.info/encyclopedia/ETEmain.html)
Seed: Science is Culture (http://seedmagazine.com/)
Science-a-gogo (http://www.scienceagogo.com/)
Science Gems (http://www.sciencegems.com/)
Science Learning Network (http://www.sln.org/)
Extreme Science (http://www.extremescience.com/)
The Yuckiest Site on the Internet (http://yucky.discovery.com/flash/)
Sci Network (http://madsci.org/)
Junk Science (http://junkscience.com/)
William H. Calvin (http://williamcalvin.com/)
Max Tegmark's Homepage (http://space.mit.edu/home/tegmark/index.html)