What is Blogging?
A blog (a contraction of the term weblog) is a type of website, usually maintained by an individual with regular entries of commentary, descriptions of events, or other material such as graphics or video. Entries are commonly displayed in reverse-chronological order. "Blog" can also be used as a verb, meaning to maintain or add content to a blog.
(Source: http://en.wikipedia.org/wiki/BLOG)

Why Blog as a teacher?
http://edublogs.org/10-ways-to-use-your-edublog-to-teach/

Why Blog with your class?
http://edublogs.org/tags/?t=maths
the why we do maths issue - http://www.squidoo.com/ymath

Journalling in Maths:
http://arb.nzcer.org.nz/supportmaterials/maths/journalling.php