Typealyzer is a fun site where you can have the writing on your blog analysed!
It also shows you what parts of the brain were dominant during the writing.
Children would have a lot of fun having a look at this. I tried how it would work by using a class blog - it would be a lot of fun for children. I wonder if it would change during the year, for example when the teacher originally set up the site and then as children added to it.