At its most basic blogging is done for the purpose of quickly and easily distributing information to others. In the context of education this means distributing information to students and their parents. That information could be anything from assignment due dates to course notes to articles and videos that supplement your classroom instruction. Here's a cartoon explanation that I made about one of the benefits of teachers having blogs.
This is where blogging becomes more than just an exercise in disseminating information. As a teacher you can post prompts to which your students write replies in the form of comments. Better yet, make students authors on a blog and have them post prompts for their classmates to respond to. The prompts could be in the form of a reflection written by a student, a thought-provoking article from the web accompanied by questions, an image, a video, or perhaps an embedded VoiceThread.
The great thing about using blogs for classroom discussions is that it provides students with more time to reflect on what they're being asked before sharing their responses. Blog discussions also provides a forum for shy students to express themselves with written words instead of possibly staying out of a in-classroom conversation.
By making students authors on a group blog or by having them maintain their own individual blogs they can demonstrate what they've found through research, what they learned, and what they have created to demonstrate their learning. In other words, your students' blogs become digital portfolios of what they have done in your classroom. One of the benefits of putting these portfolios on the web is that other students can view and learn from them. Another benefit is that now other teachers, school administrators, and your students' families can quickly discover the great work your students have done.
If you're wondering about the picture, it's of my newly adopted dog Max. I just wanted to include a picture of him in a blog post. This was the first time that he was relaxed enough to actually nap in his new home.