Catkin is blogging tool. It will help you maintain a weblog or journal site. Features include a web interface, threaded comments and a flexible templating system. It is written in Perl and runs on the webserver.
Catkin is currently at an early stage in its development. I wouldn't encourage people to use it unless they are familiar with Perl and CGI and are willing to deal with bugs and changing file formats as the system matures.
For an example of a real site using Catkin see Words by c.z.robertson.