I found a few good websites that focus on using blogs in school, at a variety of levels:
Everything listed on these and similar pages will be wonderful if/when school systems allow access to blogs. During Seminar when we were required to read/submit to a blog, access to the site was blocked. I contacted the Web Administrator for the county and had the page unblocked. Unfortunatey, that only gave me access the the blog's homepage, and none of the comments of ability to comment myself.
School systems have a ways to go before they have a good grasp on blogs, and how to use them even if many of their teachers already do.