Another good physics-related blog that is not mentioned is https://gravityandlevity.wordpress.com/ by Brian Skinner. While it's not that active anymore, it has some really nice explanations of various concepts in physics.
One of my favourite science blogs (unfortunately relatively inactive over the past year or so) is Three Toed Sloth (https://bactra.org/weblog) by physicist-turned-statistician Cosma Shalizi, due to the breadth and the range of topics he covers (from physics to statistics to complex systems to the social sciences).
Related to his blog is his Notebooks, which is a collection of books, articles, and websites of a wide range of topics on science and others;
As this has been somewhat expanded to also include help sites, I feel comfortable mentioning Math Help Boards.
Some of the discussions there would fit well in a blog, and it deserves more traffic.
Last year, there was an informal cooperation with PF to provide math challenge problems (see here and scroll down).
It was coordinated by @Ackbach .
(Note: I just post there sometimes - like certain others here - and am not otherwise affiliated.)