Teaching Montana History http://teachingmontanahistory.blogspot.com/ by Martha Kohl. Is another favorite blog. She shares lots of resources, many that would be applicable to other parts of the country.
Teaching History. org http://teachinghistory.org/ is a site I'm sure many are already familiar with. If not block out some time and enjoy. It is a site that I go to frequently. The History Project http://historyproject.ucdavis.edu/ is full of resources for teachers.
I've already shared Montana Moments http://ellenbaumler.blogspot.com/ by Ellen Baumler. I lover her humor. It always amazes me the gems she shares.