Your favorite Physics/Astrophysics blogs? What are the Physics/Astrophysics blogs you regularly read? I'm looking to beef up my RSS feeds to catch up with during my long commutes. I'd like to discover lesser-known gems (e.g. not well known blogs such as Cosmic Variance), possibly that are updated regularly and recently.
Since this is a list, give one entry per answer please. Feel free to post more than one answer.
 A: My personal blog is
Arcsecond

It's not exclusively physics.  Since it's a personal blog, it's about whatever interests me at the moment.  When I do write about physics, the level is usually undergraduate (since that's my education level).  I usually update in irregular bursts.
Some example posts:
Physics
Viete's Formula and Spinning Pizza
Uses simple physics to derive Viete's Formula 
$$\frac{2}{\pi} = \frac{\sqrt{2}}{2}\cdot\frac{\sqrt{2+\sqrt{2}}}{2}\cdot\frac{\sqrt{2+\sqrt{2+\sqrt{2}}}}{2}\cdots$$
Fucking Geomagnetism, How Does That Work? 
Response to Cosmic Variance's essay on Insane Clown Posse's "Miracles" video.
Bounce, part 2 
Why won't a ball bounce higher than it's dropped?
Math
The Power Tower
What is $\sqrt{2}$ taken to the power of itself, over and over?
Answer, Lemming
A very cute puzzle from Ravi Vakil's "A Mathematical Mosaic".
Memoir
Why I Rode a Bicycle 200 Miles The Other Day
Pulse
Essay
'Simple' Isn't 'Easy'
Humor
Have You Ever Noticed A Panda Is Just a Fat, Slow Zebra?
Why I Don't Drink Soda
A Review of Reviews of Racism and a Very Sexy Reimagining
Comic
Sine Error: Spare Me
Sine Error: Tricked You!
A: Resonances
Another best place for detailed reports on new particle physics discoveries (and rumours)
A: US LHC Blogs
A number of US scientists who work on the LHC explain various topics in physics. One particularly good series of posts is titled "Let's Draw Feynman diagrams!"
A: A Quantum Diaries Survivor
The best place for detailed reports on new particle physics discoveries (and rumours)
A: Uncertain Principles
Chad Orzel is awesome. Good stuff on AMO and sci-fi.
A: Starts With a Bang
Similar in tone and style to Cosmic Variance with entertaining in-depth posts on various subjects in astrophysics and cosmology, including an excellent 8 part series on the history of the universe called "The Greatest Story Ever Told"
A: Ellipsix Informatics
Since a few other people have posted their own blogs, I thought it wouldn't be inappropriate for me to do the same. This is my personal website, not a dedicated physics blog, but the posts I make about physics and/or information technology are the current "main attraction." The posts are based on whatever I happen to be thinking about when I have time to write something. Mostly I like to focus on applications of physics to everyday life (i.e. situations that would arise outside a lab).
Probably the best posts are the ones about Mythbusters episodes, e.g.


*

*http://www.ellipsix.net/blog/2010/12/death-rays-and-thermal-radiation.html

*http://www.ellipsix.net/blog/2010/04/calculating-terminal-speed.html

*http://www.ellipsix.net/blog/2010/01/bouncing-bullets.html
I also have an associated Twitter account where I post assorted physics/astronomy-related links.
https://twitter.com/ellipsix
A: Dot Physics
This deals with popular topics from the perspective of an actual physicist (so, a lot of rants about instances when non-specialists get things wrong, and occasionally praise for when they get it right). It won't strain your brain, but I always find the posts to be fun to read, and pretty insightful. 
A: The Hammock Physicist
Ok, time for some shameless self-promotion:
Like most science blogs, this blog focuses on an interested lay audience. I try to explain common misunderstandings, often by elucidating the physics with simple models and (animated) visuals. See for instance 'Fibonacci Chaos', 'God, Godel, Gravity' and 'Less Is More'.
A: Ars Physica
Although mostly in brazilian portuguese (pt_BR — even though in the days of Google Translate i don't know how big a problem this actually represents ;-), it's a collective effort including high energy theorists and experimentalists, condensed matter theorists, and neuroscientists.
So, the topic selection is quite varied, and so is the level of presentation: from popularization pieces all the way to full fledged research.
A: Symmetry Breaking
an excellent general physics blog created by Fermilab and SLAC. 
A: The Big Blog Theory
This is the blog of UCLA physicist David Saltzberg, who is the scientific advisor to the CBS sitcom The Big Bang Theory. The science (derived from the episodes) is simple. But you still can find some interesting stuff.
A: Of Particular Significance
Matt Strassler's blog on particle physics. This is aimed at being accessible to the public, but he incorporates a lot of graphs and a decent amount of technical detail. The site gets updated almost daily with either general articles about particle physics, or news of recent developments.
A: The Reference Frame
it is the only one that is challenging.
A: John Baez's Stuff
It is more mathematics, but a lot of physics/mathematical physics related "stuff" also.
A: Cosmic Variance
Science, Technology, and The Future
NOTE It would be great if someone who knows the blog well would write a few words about it. Just give a little more detail of what it's about. 3 sentences is more than enough. This is community wiki, so most people can edit it freely.
A: AstroBetter
Tips and Tricks for Professional Astronomers
A: Skulls in the Stars
Exceptional for its extremely clear, basic-level introductions to phenomena in optics I would otherwise never have heard of, and for interesting historical posts resulting from digging around in the archives of old journals and scientists' personal letters.
A: Astronomy Cast
this is actually a podcast, not a blog, but it is still fantastic. Two hosts, one a blogger, one an astrophysics go over various topics in astronomy, physics and cosmology. I particularly liked the "History of Astronomy" series, but the posts on current discoveries are just as good. 
A: 
Cocktail Party Physics
Jennifer Ouellette, spousal unit of Sean Carroll, organized this and has some of her female friends writing guest blogs on rotation.
The topics are mostly physics with a discursive and historical slant, and are at popular level. Jennifer is an intelligent English major who writes science well. I threw this in both because the writing is good, but also hopefully to attract more females to physics stack. Now that I have disclosed my motivation, my real favorite blog has to be The Reference Frame for its virtuoso physics 
improvisations by Lubos.
A: Condensed Concepts is a great blog, and the only one I've found that deals with Condensed Matter Physics directly.  I would be interested to hear if there are others.
A: Why I hate physics
Congratulations Marty Green.
Give me (us) more, pls.  
A: Technology Review, arXiv blog
The newest and most interesting posting from arXiv with summary and figures.
A: Phys.org
It's specific but easy to read.
