I don't know if this is possible, but could be useful for inspiring students to write more. (Our teachers assign blogging as part of their English as a second language courses.)

In a block, perhaps similar to the "Quiz Results" block, have the top 5 bloggers listed along with the number of blog entries.

For example: (With the number of entries).

TOP 5 BLOGGERS
John Smith (245)
Jane White (136)
Joe Winters (136)
Bill Jackson (115)
Sue Johnson (89)

Or perhaps, with the number of words.

TOP 5 BLOGGERS
John Smith (34,003)
Jane White (13,345)
Joe Winters (11,36)
Bill Jackson (9,115)
Sue Johnson (989)

You could, perhaps, have the students names clickable going directly to their blog entries instead of to their profiles.

Perhaps, like the "Quiz Results" block, you could make this configurable, even allowing teachers to display the "Bottom 5 Bloggers." And further configurable, to allow the teacher to choose the number of students to be displayed.