Maybe this is news to you, or maybe it is not, but Fawn Nguyen has a really nice blog about math teaching and miscellanies.
I am kind of a blog junkie, and have always been. To me, what type of content makes a teaching blog nice? --Specific discussion about activities, and why they structure them as such. Honestly, I am too concrete a thinker (and am generally too busy) to read abstract, philosophical discussions that do not give specific illustrations. Personally, I also appreciate it when bloggers don't complain continuously about the same thing, because I believe that we all have our reasons to be negative, so there is no reason to dump our own negativity onto others. I think it's a nice rule of thumb to say that if you point out that something doesn't work or isn't ideal (which is fair to do from time to time), that you must offer a concrete alternative that could be feasible and more effective. Our school admin mentioned this in the beginning of the year as a general courtesy to keep at staff meetings; I try to keep that courtesy online as well. On the receiving side, I definitely recognize teaching blogs that leave me with a heavy feeling, versus teaching blogs that make me feel inspired and happy.
Fawn's blog is specific, positive, and it also shares some personal tidbits, which is also nice. I personally enjoy it when someone's blog goes a little bit beyond the teaching and shares a little about their own lives, because if I care about their teaching, inevitably I start caring about their lives as well...
Another blog that I also think is very nice (but that has been around now for a little while now, actually) is Amy Gruen's Square Root of Negative One Teach Math. Amy's blog is not pretentious and is altogether lovely, and her love for her students shines through effortlessly.
Also, the awesome Tina Cardone is as fun online as she is in person!
Enjoy! If your affinity for blogs matches mine (in terms of what type of content you prefer), I would love it if you could comment and leave me with a few suggestions of new blogs to follow.