The reason why I consider blogs an excellent tool for the classroom is that they offer easy access to a great variety of resources. These are especially selected or created by each teacher to fit the needs of his own students according to their level, age, preferences in content, etc.
A blog allows activities of many different types: reading, listening, music, games, powerpoint presentations, videos and so on. I often include my students' work, and this makes the blog more appealing for them.
A teacher can use a blog to offer links to useful resources, too, and these are very handy as they are always visible. The rest of the materials (those included in the different entries) are easy to find in the list of categories that you create according to your needs.
You have a wide range of layouts to choose from when you start a blog, and lots of gadgets to add to it in order to make it more attractive for your students.
As a teacher, I couldn't do without my blog now!