There are a wide variety of REASONS to blog with students in the classroom, and many options in terms of platforms to use. The biggest reason TO blog is: The more we write, the better writers we become. There are lots more!
Our classroom blog this term is a commercial (not free) blog hosted by 21classes.com. Our class blog (linked under "Resources" too) is untcic.21classes.com.
Two ways to define or categorize classroom blogs is by purpose.