There are numerous Mathematics blogs out there!
A really easy way to follow the UK education Maths blogs is to follow The Maths Echo Chamber
Try Mathblogging.org to see recent posts from an extensive collection of blogs from around the world about mathematics in all its facets.
Craig Barton who has some of his own favourite blogs (thank you for the mention Craig!) has his own blog where you will find many outstanding resources; see for example all the TES Top 10 Collections and the Resource of the Week. See also Craig’s examples from his fantastic Diagnostic Questions site.
Some more of my own favourites include Dan Meyer’s blog, Don Steward’s Median and The Reflective Educator from David Wees. From Murray Bourne, see his IntMaths newsletters and his blog. From Jo Morgan we have her quite rightly, very well known Resourceaholic, from Bruno Reddy, Mr Reddy Maths Blog, the list goes on! We also have Mel’s Just Maths, Ed Sothall’s Solve My Maths, John Golden’s Math Hombre and Dan Pearcy’s Teaching Mathematics. From K Pichford we have Maths Sandpit – some great lesson ideas there. And don’t miss Mohammed Ladak’s MathedUp! or Danielle Bartram’s blog (and resources) on Miss B Resources. and Guillermo Bautista’s ‘Mathematics and Multimedia‘. Guillermo has discussed the connection between mathematics and other fields such as the arts, music, poetry, and other sciences under the Math Palette category.
From fellow Maths TES Panel members we have Dave Gale’s Reflective Maths, Paul Collins’ Mathematics Blog. and Great Maths Teaching Ideas from William Emeny. Sharon Derbyshire and Laura Rees-Hughes’ Number Loving Blog has many great posts and there are also numerous resources available.
TES have a Mathematics blog which includes a great variety of ideas to try in the classroom.
Not strictly Mathematics blogs but I have some favourites on Teaching and Learning generally, I think these writers have something to say for teachers of any subject.