I haven't noticed anyone mention www.21classes.com yet. I use that for my sixth grade students (another teacher here uses it for seventh and eighth as well) and I find the benefit is that it can be set to be a safe, private environment. I did upgrade and begin paying a monthly fee for it, but it can be used for free as well. Their customer service is great. You can choose to make it public, but if you want your class to blog as a private group, this is a great option.
My advice is to think through why you are starting a blog for your class. The blog's purpose will probably help you identify which app you want to choose. I chose blogger because I like how powerful it is. I have created several different blogs for specific things as well.
Here is my class blog http://mrcsclassblog.blogspot.com/
Here is the blog my students post on http://mrcsclasscompendium.blogspot.com/
I am sure you are going to have fun with blogging and if you have any more questions, feel free to contact me.
Thank you for all of your input. Yes, this is something that I need to think through. I plan on implmenting my "blog" next year. I will plan it out more in detail over the summer break. I will be looking for some assistance, thanks!!