You've written dozens -- maybe even hundreds -- of essays. But what is an essay? Essays can take up just a single page (like the My Turn essay Newsweek publishes in each issue) or a whole book. "Essay" is a noun, but it's also a verb. Unfortunately, many students are rarely asked to essay when writing an essay. Spend some time thinking about and researching this question, and then offer a thoughtful, considered response. (A regurgitated dictionary definition, by the way, is not a thoughtful, considered response, but I think/hope you know that already.)
Oh, and by the way -- make sure that your blog is set up to enable others to comment. Some students have told me that they've had trouble commenting on other students' Blogger blogs, which may mean that the default settings limit commenting too much.