There are a range of other museums and cultural institutions that host blogs related to teachers and education. Here's a selection of some of them.
National Portrait Gallery, Canberra Education BlogSpace
Museum-Ed The Museum-Ed Blog. Museum-Ed is "a not-for-profit organization dedicated to providing museum educators opportunities to ask questions, to exchange ideas, to explore current issues, to share resources, to reflect on experiences, and to inspire new directions in museum education."
Museum Education Rountable Blog The blog of the Museum Education Roundtable (MER): "Network, the newsletter of the MER, is now available to all museum educators via the web. Previously a benefit of membership, the MER board voted 2/7/2007 to make the newsletter available without subscription and to migrate to a blog format."
Educator Resource Centre, Cooper-Hewitt National Design Museum. I know it's not a blog per se, but has great online resources for educators.
There is also the wonderful online resource Museumblogs.org that lists many, many museum-related blogs which is worth checking out.
What other online museum blogs/resources do you know of for teachers?