I have found a group of math teachers online who have made a really strong online community. Together, they are questioning, innovating, and making positive change happen and then sharing through blogs and tweets. It's incredibly inspiring. Anyone who is a new math or science teacher should read these blogs and follow these folks on Twitter. Get into the discussion.
Honestly, this is the best use of blogs and Twitter I have seen yet. These folks rock the house.
That said, here is a list of some of my favorite math teacher bloggers/twitterers:
Dan Meyer (@ddmeyer)
Dan has been featured on TED, so lots of people know who he is.
Kate Nowak (@k8nowak)
Hers is the best subtitle out there. I will make you click the link to read it. Go ahead. I'll wait....
Sam Shah (@samjshah)
Sam's post on the Blogotwitterversphere is great, and attaining mention on his Favorite Tweets page is a goal for every math teacher tweeter.
Matt Townsley (@mctownsley)
Like me, Matt is a former HS math teacher turned curriculum dude. His focus on assessment is a good thing.
Jason Buell (@jybuell)
Blog: Always Formative
Jason's ideas about assessment are important (and by "important" I mean that he and I agree on some key points).
BTW: To get plugged in to the flow of the conversation, check out the mathteachers list maintained by Jackie Ballarini. Great, diverse list of folks.
Note that I have left a ton of people off this list. Check out the blogs and the teacher twitter list and start roaming to find more.