There's usually not much to a blog. A table to hold the entries, a page to make entries, and a page that lists them out.
If you want people to leave comments, then again it's not that hard. A table to hold the comments and a section on your blog viewing page to add a comment. I would use some form of a captcha entry, their name, and the actual comment itself; no need to "register" to be a user.
All in all, probably a good couple hours work; which would be less than implementing someone elses stuff. Just be sure to sanitize the comments to prevent xss attacks.