Before creating a blog for your class, below are two examples that may give you some ideas.
1) The KinderKids' Blog

I came across this blog when looking for something on Eric Carle's book; The Very Hungry Caterpillar. The blog shows a variety of ways students in Early Stage 1 can make use of their new literacy skills across the KLAs. It includes students' artwork, class videos, reports of special visitors they have had in the classroom, links to websites and messages from teachers.
One of the great aspects of this blog is it shows how connected the students can be with others. This class has blogging mentors; a group of university students in Canada who they call using Skype and talk to regularly to receive feed back on how their blog is going...very cool!
2) Sunshine Coast Grammar School
This school has adopted blogging on several levels including teachers and students.

It is a bit on the formal side but a good example to show students how blogging is a useful communication tool for the school community. I would think this blog is more suitable for upper primary years or maybe school leaders. Students can see how easy it is to post friendly reminders about upcoming school events such as 'pancake day' or report on school / student achievements from sport carnivals or inter-school events.

